Telecommunications apparatus and methods

ABSTRACT

A method of operating a terminal device in a wireless telecommunications system that supports a connected mode of operation in which terminal devices receive a type user-plane data from the network infrastructure equipment using primary and/or secondary component carriers operating on different frequency bands and an idle mode of operation in which terminal devices do not receive that type of user-plane data from the network infrastructure equipment. The method includes: establishing a measurement configuration making measurements of radio channel conditions for radio resources within the second frequency band; making measurement of radio channel conditions for radio resources within the second frequency band in accordance with the measurement configuration while the terminal device is operating in the idle mode; determining if the measurement of radio channel conditions meets a trigger criterion, and if so, transmitting a measurement report to the network infrastructure equipment to indicate the trigger criterion has been met.

BACKGROUND Field

The present disclosure relates to telecommunications apparatus andmethods, for example mobile communications networks and methods forcommunicating data using mobile communications networks, infrastructureequipment for mobile communications networks, communications devices forcommunicating data via mobile communications networks and methods ofcommunicating via mobile communications networks.

Description of Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentinvention.

It is well known in the field of wireless telecommunications for regionsof the radio spectrum to be assigned to different mobile networkoperators (MNO) for their exclusive use through a license. A licensetypically grants an MNO exclusive use over a number of years of apredefined portion of the radio frequency spectrum in which to deploy amobile communications network (e.g. GSM, WCDMA/HSPA, LTE/LTE-A). Thislicensing approach can help guarantee Quality of Service (QoS) andprovides an operator with control of the radio resources and mobility.In particular, an operator has some degree of guarantee that no otherradio services should interfere with the radio resources that have beenassigned to the operator, and within the limitations of the licenseconditions the operator has exclusive control over what radio technologyit deploys in the network. Consequently, a wireless telecommunicationssystem that is primarily designed to operate using radio resources thathave been licensed for exclusive use by the wireless telecommunicationssystem can operate with a degree of centralised control and coordinationto you a full help make most efficient use of the available radioresources. Such a wireless telecommunication system can also manageinterference internally, based on standard specifications, since thelicence grants it a degree of immunity from external interferencesources. Coexistence of different devices deployed on an MNO's licensedband can be managed through conformance to relevant radio standards.Licensed spectrum is today usually assigned to operators viagovernment-organised auctions, but so-called “beauty contests” continuealso to be in use.

It is also well known in the field of wireless telecommunications forregions of the available radio spectrum to remain unlicensed. Unlicensed(licence exempt) radio spectrum may, at least to some extent, be freelyused by a number of different technologies, such as Wi-Fi and Bluetoothand other non-3GPP radio access technologies (RATs). Operatingparameters for devices using unlicensed spectrum bands are typicallystipulated by technical regulatory requirements, e.g. the FCC Part 15rule for 2.4 GHz ISM band.

Coexistence of different devices deployed on an unlicensed bandgenerally lacks centralised coordination and control and so is usuallybased on such technical rules and various politeness protocols.

The use of wireless telecommunications system technologies designed foroperation on licensed radio spectrum, such as LTE, is becoming more andmore prevalent, both in terms of increasing take-up of established usesfor wireless telecommunications technologies, and also the introductionof new uses, e.g., in the developing field of machine-typecommunications (MTC). In order to help provide more bandwidth to supportthis increased use of wireless telecommunications technologies, it hasrecently been proposed to use unlicensed radio spectrum resources tosupport operations on licensed radio spectrum.

However, in contrast to licensed spectrum, unlicensed spectrum can beshared and used among different technologies, or different networksusing the same technology, without any co-ordinated/centralised control,for example to provide protection against interference. As a consequenceof this, the use of wireless technologies in unlicensed spectrum can besubject to unpredictable interference with no guarantees of spectrumresource availability and radio connections taking place on a besteffort basis. Thus the operation of wireless network technologies onshared radio resource spectrum (such as unlicensed spectrum) can beimpacted by the operation of other radio access technologies, such aswireless local area networks, and conversely the operation of such otherradio access technologies can be impacted by the operation of thewireless network technologies on the shared portions of the radiospectrum.

For example, an LTE-based wireless telecommunications network that isable to make use of radio resources shared with a wireless local areanetwork radio access technology (WLAN) could potentially prevent a WLANaccess point from operating properly, at least temporarily. For example,certain WLAN radio access technologies, such as Wi-Fi, operate on a“listen-before-talk” basis to help manage access to the sharedresources. Basically, a device operating on the WLAN that wishes toaccess certain radio resources will first monitor the radio resources todetermine if they are currently available or already in use. AnLTE-based wireless telecommunications network may be configured to adopta similar “listen-before-talk” approach in respect of its communicationson shared radio resources to seek to avoid making transmissions onresources currently being used for WLAN communications. However, anissue with this approach can arise because of differences in typicalcoverage areas associated with WLAN access points and LTE base stations.For example, an LTE base station may be too far from a WLAN access pointto be able to detect ongoing WLAN communications associated with theWLAN access point but the WLAN access point may nonetheless be withinthe coverage area of the LTE base station downlink signals. Accordingly,a base station implementing a “listen-before-talk” approach to helpgovern its access to shared radio resources may not be able to detectcommunications associated with the WLAN access point when the basestation is monitoring the relevant radio resource usage by other devices(“listen”). Accordingly, the base station may conclude it is free totransmit (“talk”) on radio resources which are being used by the WLANaccess point, thereby interfering with the WLAN access point andpotentially making it unavailable while the LTE base station istransmitting. In some respects this may be referred to as a “hiddennode” issue.

These types of issue mean that wireless network technologies, such asLTE, which are generally designed to operate using licensed radioresources, may benefit from modified approaches to allow them toefficiently use shared radio resources, and in particular to co-existreliably and fairly with other radio access technologies accessing theshared resources. Therefore, deploying a mobile radio access technologysystem primarily designed to operate in licensed spectrum bands (i.e.having exclusive access to, and hence a level of control over, therelevant radio resources) in a manner which is required by operation ina shared/unlicensed spectrum band (i.e. without having exclusive accessto at least some of the relevant radio resources), gives rise to newtechnical challenges.

SUMMARY

According to one aspect of the present disclosure, there is provided amethod of operating a terminal device in a wireless telecommunicationssystem configured to support communications between networkinfrastructure equipment and terminal devices using a primary componentcarrier operating on radio resources within a first frequency band and asecondary component carrier operating on radio resources within a secondfrequency band, wherein the wireless telecommunications system supportsa connected mode of operation in which terminal devices receiveuser-plane data from the network infrastructure equipment using theprimary and/or secondary component carrier and an idle mode of operationin which terminal devices do not receive user-plane data from thenetwork infrastructure equipment, wherein the method comprises:establishing a measurement configuration for making measurements ofradio channel conditions for radio resources within the second frequencyband; making a measurement (assessment) of radio channel conditions forradio resources within the second frequency band in accordance with themeasurement configuration while the terminal device is operating in theidle mode; determining if the measurement of radio channel conditionsmeets a trigger criterion, and if so, transmitting a measurement reportto the network infrastructure equipment to indicate the triggercriterion has been met.

According to another aspect of the present disclosure, there is provideda terminal device for use in a wireless telecommunications systemconfigured to support communications between network infrastructureequipment and terminal devices using a primary component carrieroperating on radio resources within a first frequency band and asecondary component carrier operating on radio resources within a secondfrequency band, wherein the wireless telecommunications system supportsa connected mode of operation in which terminal devices receiveuser-plane data from the network infrastructure equipment using theprimary and/or secondary component carrier and an idle mode of operationin which terminal devices do not receive user-plane data from thenetwork infrastructure equipment, wherein the terminal device comprisesa controller unit and a transceiver unit configured to operate togetherto: establish a measurement configuration for making measurements ofradio channel conditions for radio resources within the second frequencyband; make a measurement of radio channel conditions for radio resourceswithin the second frequency band in accordance with the measurementconfiguration while the terminal device is operating in the idle mode;determine if the measurement of radio channel conditions meets a triggercriterion, and if so, transmit a measurement report to the networkinfrastructure equipment to indicate the trigger criterion has been met.

According to one aspect of the present disclosure, there is providedcircuitry for a terminal device for use in a wireless telecommunicationssystem configured to support communications between networkinfrastructure equipment and terminal devices using a primary componentcarrier operating on radio resources within a first frequency band and asecondary component carrier operating on radio resources within a secondfrequency band, wherein the wireless telecommunications system supportsa connected mode of operation in which terminal devices receiveuser-plane data from the network infrastructure equipment using theprimary and/or secondary component carrier and an idle mode of operationin which terminal devices do not receive user-plane data from thenetwork infrastructure equipment, wherein the circuitry comprises acontroller element and a transceiver element configured to operatetogether to: establish a measurement configuration for makingmeasurements of radio channel conditions for radio resources within thesecond frequency band; make a measurement of radio channel conditionsfor radio resources within the second frequency band in accordance withthe measurement configuration while the terminal device is operating inthe idle mode; determine if the measurement of radio channel conditionsmeets a trigger criterion, and if so, transmit a measurement report tothe network infrastructure equipment to indicate the trigger criterionhas been met.

According to one aspect of the present disclosure, there is provided amethod of operating network infrastructure equipment in a wirelesstelecommunications system configured to support communications betweenthe network infrastructure equipment and terminal devices using aprimary component carrier operating on radio resources within a firstfrequency band and a secondary component carrier operating on radioresources within a second frequency band, wherein the wirelesstelecommunications system supports a connected mode of operation inwhich terminal devices receive user-plane data from the networkinfrastructure equipment using the primary and/or secondary componentcarrier and an idle mode of operation in which terminal devices do notreceive user-plane data from the network infrastructure equipment,wherein the method comprises: communicating user plane-data with a firstterminal device operating in the connected mode using the primary and/orsecondary component carrier; configuring a second terminal device tomake a measurement of radio channel conditions for radio resourceswithin the second frequency band while the second terminal device isoperating in the idle mode and to determine if the measurement of radiochannel conditions meets a trigger criterion, and if so, transmit ameasurement report to the network infrastructure equipment to indicatethe trigger criterion has been met; receiving a measurement report fromthe second terminal device indicating the second terminal device hasdetermined the measurement of radio channel conditions met the triggercriterion; and modifying the communication of user-plane data with thefirst terminal device using the primary and/or secondary componentcarrier in response thereto.

According to one aspect of the present disclosure, there is providednetwork infrastructure equipment for use in a wirelesstelecommunications system configured to support communications betweenthe network infrastructure equipment and terminal devices using aprimary component carrier operating on radio resources within a firstfrequency band and a secondary component carrier operating on radioresources within a second frequency band, wherein the wirelesstelecommunications system supports a connected mode of operation inwhich terminal devices receive user-plane data from the networkinfrastructure equipment using the primary and/or secondary componentcarrier and an idle mode of operation in which terminal devices do notreceive user-plane data from the network infrastructure equipment;wherein the network infrastructure equipment comprises a controller unitand a transceiver unit configured to operate together to: communicateuser plane-data with a first terminal device operating in the connectedmode using the primary and/or secondary component carrier; configure asecond terminal device to make a measurement of radio channel conditionsfor radio resources within the second frequency band while the secondterminal device is operating in the idle mode and to determine if themeasurement of radio channel conditions meets a trigger criterion, andif so, transmit a measurement report to the network infrastructureequipment to indicate the trigger criterion has been met; receive ameasurement report from the second terminal device indicating the secondterminal device has determined the measurement of radio channelconditions met the trigger criterion; and modify the communication ofuser-plane data with the first terminal device using the primary and/orsecondary component carrier in response thereto.

According to one aspect of the present disclosure, there is providedcircuitry for a network infrastructure equipment for use in a wirelesstelecommunications system configured to support communications betweenthe network infrastructure equipment and terminal devices using aprimary component carrier operating on radio resources within a firstfrequency band and a secondary component carrier operating on radioresources within a second frequency band, wherein the wirelesstelecommunications system supports a connected mode of operation inwhich terminal devices receive user-plane data from the networkinfrastructure equipment using the primary and/or secondary componentcarrier and an idle mode of operation in which terminal devices do notreceive user-plane data from the network infrastructure equipment;wherein the circuitry comprises a controller element and a transceiverelement configured to operate together to: communicate user plane-datawith a first terminal device operating in the connected mode using theprimary and/or secondary component carrier; configure a second terminaldevice to make a measurement of radio channel conditions for radioresources within the second frequency band while the second terminaldevice is operating in the idle mode and to determine if the measurementof radio channel conditions meets a trigger criterion, and if so,transmit a measurement report to the network infrastructure equipment toindicate the trigger criterion has been met; receive a measurementreport from the second terminal device indicating the second terminaldevice has determined the measurement of radio channel conditions metthe trigger criterion; and modify the communication of user-plane datawith the first terminal device using the primary and/or secondarycomponent carrier in response thereto.

Further respective aspects and features are defined by the appendedclaims.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings wherein likereference numerals designate identical or corresponding parts throughoutthe several views, and wherein:

FIG. 1 provides a schematic diagram illustrating an example of a mobiletelecommunication system;

FIG. 2 provides a schematic diagram illustrating a LTE radio frame;

FIG. 3 provides a schematic diagram illustrating an example of a LTEdownlink radio subframe;

FIG. 4 schematically represents a wireless telecommunications systemaccording to an embodiment of the disclosure;

FIG. 5 is a signalling ladder diagram representing some operatingaspects of a base station and a terminal device in accordance with someembodiments of the disclosure; and

FIG. 6 is a signalling ladder diagram representing some operatingaspects of a base station and a terminal device in accordance with someother embodiments of the disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 provides a schematic diagram illustrating some basicfunctionality of a mobile telecommunications network/system 100operating in accordance with LTE principles and which may be adapted toimplement embodiments of the disclosure as described further below.Various elements of FIG. 1 and their respective modes of operation arewell-known and defined in the relevant standards administered by the3GPP® body, and also described in many books on the subject, forexample, Holma H. and Toskala A [1]. It will be appreciated thatoperational aspects of the telecommunications network which are notspecifically described below may be implemented in accordance with anyknown techniques, for example according to the relevant standards.

The network 100 includes a plurality of base stations 101 connected to acore network 102. Each base station provides a coverage area 103 (i.e. acell) within which data can be communicated to and from terminal devices104. Data is transmitted from base stations 101 to terminal devices 104within their respective coverage areas 103 via a radio downlink. Data istransmitted from terminal devices 104 to the base stations 101 via aradio uplink. The core network 102 routes data to and from the terminaldevices 104 via the respective base stations 101 and provides functionssuch as authentication, mobility management, charging and so on.Terminal devices may also be referred to as mobile stations, userequipment (UE), user terminal, mobile radio, communications device, andso forth. Base stations, which are an example of network infrastructureequipment, may also be referred to as transceiverstations/nodeBs/e-nodeBs, and so forth.

Mobile telecommunications systems such as those arranged in accordancewith the 3GPP defined Long Term Evolution (LTE) architecture use anorthogonal frequency division modulation (OFDM) based interface for theradio downlink (so-called OFDMA) and a single carrier frequency divisionmultiple access scheme (SC-FDMA) on the radio uplink. FIG. 2 shows aschematic diagram illustrating an OFDM based LTE downlink radio frame201. The LTE downlink radio frame is transmitted from a LTE base station(known as an enhanced Node B) and lasts 10 ms. The downlink radio framecomprises ten subframes, each subframe lasting 1 ms. A primarysynchronisation signal (PSS) and a secondary synchronisation signal(SSS) are transmitted in the first and sixth subframes of the LTE frame.A physical broadcast channel (PBCH) is transmitted in the first subframeof the LTE frame.

FIG. 3 is a schematic diagram of a grid which illustrates the structureof an example conventional downlink LTE subframe. The subframe comprisesa predetermined number of symbols which are transmitted over a 1 msperiod. Each symbol comprises a predetermined number of orthogonalsubcarriers distributed across the bandwidth of the downlink radiocarrier.

The example subframe shown in FIG. 3 comprises 14 symbols and 1200subcarriers spread across a 20 MHz bandwidth licenced for use by theoperator of the network 100, and this example is the first subframe in aframe (hence it contains PBCH). The smallest allocation of physicalresource for transmission in LTE is a resource block comprising twelvesubcarriers transmitted over one subframe. For clarity, in FIG. 3, eachindividual resource element is not shown, instead each individual box inthe subframe grid corresponds to twelve subcarriers transmitted on onesymbol.

FIG. 3 shows in hatching resource allocations for four LTE terminals340, 341, 342, 343. For example, the resource allocation 342 for a firstLTE terminal (UE 1) extends over five blocks of twelve subcarriers (i.e.60 subcarriers), the resource allocation 343 for a second LTE terminal(UE2) extends over six blocks of twelve subcarriers (i.e. 72subcarriers), and so on.

Control channel data can be transmitted in a control region 300(indicated by dotted-shading in FIG. 3) of the subframe comprising thefirst “n” symbols of the subframe where “n” can vary between one andthree symbols for channel bandwidths of 3 MHz or greater and where “n”can vary between two and four symbols for a channel bandwidth of 1.4MHz. For the sake of providing a concrete example, the followingdescription relates to host carriers with a channel bandwidth of 3 MHzor greater so the maximum value of “n” will be 3 (as in the example ofFIG. 3). The data transmitted in the control region 300 includes datatransmitted on the physical downlink control channel (PDCCH), thephysical control format indicator channel (PCFICH) and the physical HARQindicator channel (PHICH). These channels transmit physical layercontrol information. Control channel data can also or alternatively betransmitted in a second region of the subframe comprising a number ofsubcarriers for a time substantially equivalent to the duration of thesubframe, or substantially equivalent to the duration of the subframeremaining after the “n” symbols. The data transmitted in this secondregion is transmitted on the enhanced physical downlink control channel(EPDCCH). This channel transmits physical layer control informationwhich may be in addition to that transmitted on other physical layercontrol channels.

PDCCH and EPDCCH contain control data indicating which subcarriers ofthe subframe have been allocated to specific terminals (or all terminalsor subset of terminals). This may be referred to as physical-layercontrol signalling/data. Thus, the PDCCH and/or EPDCCH data transmittedin the control region 300 of the subframe shown in FIG. 3 would indicatethat UE1 has been allocated the block of resources identified byreference numeral 342, that UE2 has been allocated the block ofresources identified by reference numeral 343, and so on.

PCFICH contains control data indicating the size of the control region(i.e. between one and three symbols for channel bandwidths of 3 MHz orgreater and between two and four symbols for channel bandwidths of 1.4MHz).

PHICH contains HARQ (Hybrid Automatic Request) data indicating whetheror not previously transmitted uplink data has been successfully receivedby the network.

Symbols in a central band 310 of the time-frequency resource grid areused for the transmission of information including the primarysynchronisation signal (PSS), the secondary synchronisation signal (SSS)and the physical broadcast channel (PBCH). This central band 310 istypically 72 subcarriers wide (corresponding to a transmission bandwidthof 1.08 MHz). The PSS and SSS are synchronisation signals that oncedetected allow a LTE terminal device to achieve frame synchronisationand determine the physical layer cell identity of the enhanced Node Btransmitting the downlink signal. The PBCH carries information about thecell, comprising a master information block (MIB) that includesparameters that LTE terminals use to properly access the cell. Datatransmitted to terminals on the physical downlink shared channel(PDSCH), which may also be referred to as a downlink data channel, canbe transmitted in other resource elements of the subframe. In generalPDSCH conveys a combination of user-plane data and non-physical layercontrol-plane data (such as Radio Resource Control (RRC) and Non AccessStratum (NAS) signalling). The user-plane data and non-physical layercontrol-plane data conveyed on PDSCH may be referred to as higher layerdata (i.e. data associated with a layer higher than the physical layer).

FIG. 3 also shows a region of PDSCH containing system information andextending over a bandwidth of R344. A conventional LTE subframe willalso include reference signals which are not shown in FIG. 3 in theinterests of clarity.

The number of subcarriers in a LTE channel can vary depending on theconfiguration of the transmission network. Typically this variation isfrom 72 sub carriers contained within a 1.4 MHz channel bandwidth to1200 subcarriers contained within a 20 MHz channel bandwidth (asschematically shown in FIG. 3). As is known in the art, data transmittedon the PDCCH, PCFICH and PHICH is typically distributed on thesubcarriers across the entire bandwidth of the subframe to provide forfrequency diversity.

The communications between the base stations 101 and the terminaldevices 104 are conventionally made using radio resources that have beenlicensed for exclusive use by the operator of the network 100. Theselicensed radio resources will be only a portion of the overall radiospectrum. Other devices within the environment of the network 100 may bewirelessly communicating using other radio resources. For example, adifferent operator's network may be operating within the samegeographical region using different radio resources that have beenlicensed for use by the different operator. Other devices may beoperating using other radio resources in an unlicensed radio spectrumband, for example using Wi-Fi or Bluetooth technologies.

As noted above, it has been proposed that a wireless telecommunicationsnetwork using radio resources in a licensed portion of the radiospectrum might be supported by using radio resources in an unlicensedportion of the radio spectrum (i.e. a portion of the radio spectrum overwhich the wireless telecommunications network does not have exclusiveaccess, but rather which is shared by other access technologies and/orother wireless telecommunications networks). In particular, it has beenproposed that carrier aggregation based techniques may be used to allowunlicensed radio resources to be used in conjunction with licensed radioresources.

In essence, carrier aggregation allows for communications between a basestation and a terminal device to be made using more than one carrier.This can increase the maximum data rate that may be achieved between abase station and a terminal device as compared to when using only onecarrier and can help enable more efficient and productive use offragmented spectrum. Individual carriers that are aggregated arecommonly referred to as component carriers (or sometimes simplycomponents). In the context of LTE, carrier aggregation was introducedin Release 10 of the standard. In accordance with the current standardsfor carrier aggregation in an LTE-based system, up to five componentcarriers can be aggregated for each of downlink and uplink. Thecomponent carriers are not required to be contiguous with one anotherand can have a system bandwidth corresponding to any of the LTE-definedvalues (1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz), therebyallowing a total bandwidth of up to 100 MHz. Of course it will beappreciated this is just one example of a specific carrier aggregationimplementation and other implementations may allow for different numbersof component carriers and/or bandwidths.

Further information on the operation of carrier aggregation in thecontext of LTE-based wireless telecommunications systems can be found inthe relevant standards documents, such as ETSI TS 136 211 V 11.5.0(2014-01)/3GPP TS 36.211 version 11.5.0 Release 11 [2], ETSI TS 136 212V 11.4.0 (2014-01)/3GPP TS 36.212 version 11.4.0 Release 11 [3]; ETSI TS136 213 V 11.6.0 (2014-03)/3GPP TS 36.213 version 11.6.0 Release 11 [4];ETSI TS 136 321 V 11.5.0 (2014-03)/3GPP TS 36.321 version 11.5.0 Release11 [5]; and ETSI TS 136 331 V 11.7.0 (2014-03)/3GPP TS 36.331 version11.7.0 Release 11 [6].

In accordance with the terminology and implementation used for carrieraggregation in the context of an LTE-based system, a cell is denoted the‘primary cell’, or Pcell, for a terminal device if it is the cell thatis initially configured during connection setup for the terminal device.Thus the primary cell handles RRC (radio resource control) connectionestablishment/re-establishment for the terminal device. The primary cellis associated with a downlink component carrier and an uplink componentcarrier (CoC). These may sometimes be referred to herein as primarycomponent carriers. A cell that is configured for use by the terminaldevice after initial connection establishment on the Pcell is termed a‘secondary cell’, or Scell. Thus the secondary cells are configuredafter connections establishment to provide additional radio resources.The carriers associated with Scells may sometimes be referred to hereinas secondary component carriers. Since in LTE up to five componentcarriers can be aggregated, up to four Scells (correspondinglyassociated with up to four secondary component carriers) can beconfigured for aggregation with the primary cell (associated with theprimary component carrier). An Scell might not have both a downlink anduplink component carrier and the association between uplink componentcarriers and downlink component carriers is signalled in SIB2 on eachdownlink component carrier. The primary cell supports PDCCH and PDSCH ondownlink and PUSCH and PUCCH on uplink whereas the secondary cell(s)support PDCCH and PDSCH on downlink and PUSCH on uplink, but not PUCCH.Measurement and mobility procedures are handled on the Pcell and thePcell cannot be de-activated. The Scell(s) may be dynamically activatedand deactivated, for example according to traffic needs, though MAClayer signalling to the terminal device. An Scells for a terminal devicemay also be deactivated automatically (time out) if the terminal devicedoes not receive any transmission resource allocations on the Scell fora threshold amount of time.

Some aspects of physical layer control signalling for an LTE-basedimplementation of carrier aggregation based on the current standards arenow described.

Each downlink component carrier has the normal LTE control channels:(E)PDCCH, PCFICH and PHICH. However, carrier aggregation introduces thepossibility of so-called cross-carrier scheduling (XCS) on PDCCH. Tosupport cross-carrier scheduling, a downlink control information (DCI)message on PDCCH includes a carrier indicator field (CIF) comprisingthree bits to indicate which of the component carriers the PDCCH messageapplies to. If there is no CIF, the PDCCH is treated as applying to thecarrier on which it is received. A motivation for providingcross-carrier scheduling primarily applies for heterogeneous network(het-net) scenarios where overlaid macro- and small-cells may operatecarrier aggregation in the same band. The effects of interferencebetween the respective macro- and small-cells' PDCCH signalling can bemitigated by having the macro-cell transmit its PDCCH signalling on onecomponent carrier at relatively high transmit power (to provide coverageacross the macro-cell), while the small-cells use an alternativecomponent carrier for their PDCCH scheduling.

The control region supporting PDCCH may differ in size (i.e. number ofOFDM symbols) between component carriers, so they can carry differentPCFICH values. However, the potential for interference in the controlregion in a het-net implementation may mean that PCFICH cannot bedecoded on a particular component carrier. Therefore, current LTEstandards allow for each component to carrier a semi-static indicationof which OFDM symbol PDSCH can be assumed to begin in each subframe. Iffewer OFDM symbols are actually used for the control region, thefree/spare OFDM symbol(s) may be used for PDSCH transmissions toterminal devices which are not being cross-carrier scheduled as theywill decode the actual PCFICH. If more OFDM symbols actually used forthe control region, there will be some degree of performance degradationfor the cross-carrier scheduled terminal devices.

PHICH signalling is sent on the downlink component carrier that sent thePDCCH signalling containing the PUSCH allocation to which the PHICHsignalling relates. Accordingly, one downlink component carrier maycarry PHICH for more than one component carrier.

In the uplink, the basic operation of PUCCH is not altered by theintroduction of carrier aggregation. However, a new PUCCH format (format3) is introduced to support the sending of acknowledgement signalling(ACK/NACK signalling) for multiple downlink component carriers, and withsome alterations to format 1b to increase the number of ACK/NACK bits itcan carry.

In current LTE-based carrier aggregation scenarios, primary andsecondary synchronisation signalling (PSS and SSS) are transmitted onall component carriers using the same physical-layer cell identity (PCI)and component carriers are all synchronised with one another. This canhelp with cell search and discovery procedures. Issues relating tosecurity and system information (SI) are handled by the Pcell. Inparticular, when activating an Scell, the Pcell delivers the relevant SIfor the Scell to the terminal device using dedicated RRC signalling. Ifthe system information relating to a Scell changes, the Scell isreleased and re-added by Pcell RRC signalling (in one RRC message).Pcell changes, e.g. due to long-term fluctuations in channel qualityacross the Pcell bandwidth, are handled using a modified handoverprocedure. The source Pcell passes all the relevant carrier aggregation(CA) information to the target Pcell so the terminal device can begin touse all the assigned component carriers when handover is complete.

Random access procedures are primarily handled on the uplink componentcarrier of Pcell for a terminal device, although some aspects ofcontention resolution signalling may be cross-carrier scheduled toanother serving cell (i.e. an Scell).

As noted above, carrier aggregation is one approach for making use ofunlicensed radio spectrum resources in wireless communication networkswhich are primarily designed to use licensed radio spectrum. In broadsummary, a carrier aggregation based approach may be used to configureand operate a first component carrier (e.g. a primary component carrierassociated with a Pcell in LTE terminology) within a region of the radiospectrum that has been licensed for use by a wireless telecommunicationsnetwork, and to also configure and operate one or more further componentcarriers (e.g. a secondary component carrier associated with an Scell inLTE terminology) in an unlicensed region of the radio spectrum. Thesecondary component carrier(s) operating in the unlicensed region of theradio spectrum may do so in an opportunistic manner by making use of theunlicensed radio resources when they are available. There may also beprovisions made for restricting the extent to which a given operator canmake use of the unlicensed radio resources, for example by defining whatmight be referred to as politeness protocols.

Although known carrier aggregation schemes can form a basis for usingunlicensed radio spectrum resources (or other forms of shared radioresources) in conjunction with licensed radio spectrum resources, somemodifications to known carrier aggregation techniques may be appropriateto help optimise performance. This is because radio interference in theunlicensed radio spectrum can be expected to be subject to a wider rangeof unknown and unpredictable variations in time and frequency than mightbe seen within a region of the radio spectrum which has been licensedfor use by a particular wireless applications system. For a givenwireless telecommunications system operating in accordance with a giventechnology, such as LTE-A (Long Term Evolution Advanced), interferencein the unlicensed radio spectrum may arise from other systems operatingusing the same technology, or from systems operating according todifferent technologies, such as Wi-Fi or Bluetooth.

FIG. 4 schematically shows a telecommunications system 400 according toan embodiment of the disclosure. The telecommunications system 400 inthis example is based broadly on a LTE-type architecture. As such manyaspects of the operation of the telecommunications system 400 arestandard and well understood and not described here in detail in theinterest of brevity. Operational aspects of the telecommunicationssystem 400 which are not specifically described herein may beimplemented in accordance with any known techniques, for exampleaccording to the established LTE-standards and known variations thereof.

The telecommunications system 400 comprises a core network part (evolvedpacket core) 402 coupled to a radio network part. The radio network partcomprises a base station (evolved-nodeB) 404, a first terminal device406 a, a second terminal device 406 b and a third terminal device 406 c(which may be referred to collectively as terminal devices 406). It willof course be appreciated that in practice the radio network part maycomprise a plurality of base stations serving a larger number ofterminal devices across various communication cells. However, only asingle base station 404 and three terminal devices 406 are shown in FIG.4 in the interests of simplicity.

Although not part of the telecommunications system 400 itself, alsoshown in FIG. 4 are some other devices which are operable to wirelesslycommunicate with one another and which are operating within the radioenvironment of the telecommunications system 400. In particular, thereis a pair of wireless access devices 416 communicating with one anothervia radio link 418 operating in accordance with a Wi-Fi standard and apair of Bluetooth devices 420 communicating with one another via radiolink 422 operating in accordance with a Bluetooth standard. These otherdevices represent a potential source of radio interference andcompetition for resources for the telecommunications system 400 and viceversa. It will be appreciated that in practice there will typically bemany more such devices operating in the radio environment of thewireless telecommunications system 400, and only two pairs of devices416, 418 are shown in FIG. 4 for simplicity.

As with a conventional mobile radio network, the terminal devices 406are arranged to wirelessly communicate data to and from the base station(transceiver station) 404. The base station is in turn communicativelyconnected to a serving gateway, S-GW, (not shown) in the core networkpart which is arranged to perform routing and management of mobilecommunications services to the terminal devices 406 in thetelecommunications system 400 via the base station 404. In order tomaintain mobility management and connectivity, the core network part 402also includes a mobility management entity (not shown) which manages theenhanced packet service, EPS, connections with the terminal devices 406operating in the communications system based on subscriber informationstored in a home subscriber server, HSS. Other network components in thecore network (also not shown for simplicity) include a policy chargingand resource function, PCRF, and a packet data network gateway, PDN-GW,which provides a connection from the core network part 402 to anexternal packet data network, for example the Internet. As noted above,the operation of the various elements of the communications system 400shown in FIG. 4 may be broadly conventional apart from where modified toprovide functionality in accordance with embodiments of the disclosureas discussed herein.

The terminal devices 406 a, 406 b, 406 c each comprise a respectivetransceiver unit 407 a, 407 b, 407 c (which may be collectively referredto as transceiver units 407) for transmission and reception of wirelesssignals and respective controller units 408 a, 408 b, 408 c (which maybe collectively referred to as controller units 408) configured tocontrol the operation of the respective devices 406 in accordance withembodiments of the disclosure. The respective controller units 408 mayeach comprise a processor unit which is suitably configured/programmedto provide the desired functionality described herein using conventionalprogramming/configuration techniques for equipment in wirelesstelecommunications systems. For each of the terminal devices 406, theirrespective transceiver units 407 and controller units 408 areschematically shown in FIG. 4 as separate elements for ease ofrepresentation. However, it will be appreciated that for each terminaldevice 406 the functionality of these units can be provided in variousdifferent ways, for example using a single suitably programmed generalpurpose computer, or suitably configured application-specific integratedcircuit(s)/circuitry, or using a plurality of discretecircuitry/processing elements for providing different elements of thedesired functionality. It will be appreciated the terminal devices 406will in general comprise various other elements associated with theiroperating functionality in accordance with established wirelesstelecommunications techniques (e.g. a power source, possibly a userinterface, and so forth).

As has become commonplace in the field of wireless telecommunications,terminal devices may support Wi-Fi and Bluetooth functionality inaddition to cellular/mobile telecommunications functionality. Thus thetransceiver units 407 of the respective terminal devices may comprisefunctional modules operable according to different wirelesscommunications operating standards. For example, the terminal devices'respective transceiver units 407 may each comprise an LTE transceivermodule for supporting wireless communications in accordance with anLTE-based operating standard, a WLAN transceiver module for supportingwireless communications in accordance with a WLAN operating standard(e.g. a Wi-Fi standard), and a Bluetooth transceiver module forsupporting wireless communications in accordance with a Bluetoothoperating standard. The underlying functionality of the differenttransceiver modules may be provided in accordance with conventionaltechniques. For example, a terminal device may have separate hardwareelements to provide the functionality of each transceiver module, oralternatively, a terminal device might comprise at least some hardwareelements which are configurable to provide some or all functionality ofmultiple transceiver modules. Thus the transceiver units 407 of theterminal devices 406 represented in FIG. 4 are assumed here to providethe functionality of an LTE transceiver module, a Wi-Fi transceivermodule and a Bluetooth transceiver module in accordance withconventional wireless communications techniques.

The base station 404 comprises a transceiver unit 403 for transmissionand reception of wireless signals and a controller unit 405 configuredto control the base station 404. The controller unit 405 may comprise aprocessor unit which is suitably configured/programmed to provide thedesired functionality described herein using conventionalprogramming/configuration techniques for equipment in wirelesstelecommunications systems. The transceiver unit 403 and the controllerunit 405 are schematically shown in FIG. 4 as separate elements for easeof representation. However, it will be appreciated that thefunctionality of these units can be provided in various different ways,for example using a single suitably programmed general purpose computer,or suitably configured application-specific integratedcircuit(s)/circuitry or using a plurality of discretecircuitry/processing elements for providing different elements of thedesired functionality. It will be appreciated the base station 404 willin general comprise various other elements associated with its operatingfunctionality. For example, the base station 404 will in generalcomprise a scheduling entity responsible for scheduling communications.The functionality of the scheduling entity may, for example, be subsumedby the controller unit 405.

Thus, the base station 404 is configured to communicate data with theterminal devices 406 a, 406 b, 406 c over respective radio communicationlinks 410 a, 410 b, 410 c (which may be collectively referred to asradio communication links 410). The wireless telecommunications system400 supports a carrier aggregation mode of operation in which radiocommunication links 410 comprise a wireless access interface provided bymultiple component carriers. For example, each radio communication linkmay comprise a primary component carrier and one or more secondarycomponent carriers. Furthermore, the elements comprising the wirelesstelecommunications system 400 in accordance with this embodiment of thedisclosure are assumed to support carrier aggregation in an unlicensedspectrum mode. In this unlicensed spectrum mode the base station 404communicates with terminal devices 406 using a primary component carrieroperating on radio resources within a first frequency band that has beenlicensed for use by the wireless telecommunications system and one ormore secondary component carriers operating on radio resources within asecond frequency band that has not been licensed for exclusive use bythe wireless telecommunications system. The first frequency band maysometimes be referred to herein as a licensed frequency band and thesecond frequency band may sometimes be referred to herein as anunlicensed (U) frequency band. In the context of an LTE-based wirelesstelecommunications system, such as that represented in FIG. 4, operationin the unlicensed frequency band may sometimes be referred to as anLTE-U mode of operation. The first (licenced) frequency band may bereferred to as an LTE band (or more particularly an LTE-A band) and thesecond (unlicensed) frequency band may be referred to as an LTE-U band.Resources on the LTE-U band may be referred to as U-resources. Aterminal device able to make use of U-resources may be referred to as aU-terminal device (or U-UE). More generally, the qualifier “U” may beused herein to conveniently identify operations in respect of afrequency band comprising radio resources that may be accessed by aplurality of wireless communications systems (i.e. what might frequentlybe an unlicensed frequency band). Using shared radio resources tosupport communications in a wireless telecommunications system in thisway may also be sometimes referred to as licensed assisted access, LAA.

It will be appreciated that the use of carrier aggregation techniquesand the use of unlicensed spectrum resources (i.e. resources that may beused by other devices without centralised coordination) in accordancewith embodiments of the disclosure may be based generally aroundpreviously proposed principles for such modes of operation, for exampleas discussed above, but with modifications as described herein toprovide additional functionality in accordance with embodiments of thepresent disclosure. Accordingly, aspects of the carrier aggregation andshared spectrum (e.g. licensed assisted access) operation which are notdescribed in detail herein may be implemented in accordance with knowntechniques.

Modes of operation for the wireless telecommunications network 400represented in FIG. 4 in accordance with certain embodiments of thedisclosure will now be described. Two main scenarios will be describedwith reference to FIGS. 5 and 6. However, it will be appreciated thevarious aspects and features of the scenarios represented in FIGS. 5 and6 may be combined in accordance with some embodiments of the disclosure.That is to say, wireless telecommunications systems in accordance withcertain embodiments of the disclosure may incorporate the functionalitydescribed herein with reference to both FIGS. 5 and 6 while certainother embodiments may not incorporate some aspects of the functionalitydescribed herein with reference to FIGS. 5 and/or 6.

The general scenario represented in FIG. 5 is one in which the wirelesstelecommunications system 400 is configured to support LAA (LTE-U)operations. The LLA operation may be based on any previously proposedscheme but with modifications to provide functionality in accordancewith embodiments of the disclosure as described herein. Thus the system400 supports communications between the base station 404 and carrieraggregation capable terminal devices 406 using a primary componentcarrier (LTE-A carrier) operating on radio resources within a firstfrequency band and a secondary component carrier (LTE-U/LAA carrier)operating on radio resources within a second frequency band. Inaccordance with certain embodiments of the disclosure, the terminaldevices 406 are configured for measurement reporting in respect of radiochannel conditions for radio resources within the second frequency bandwhich the base station is using (or may wish to use) for communicatingon the secondary component carrier with one or more of the terminaldevices in an unlicensed (shared) portion of the radio spectrum. Thebase station may thus, for example, take account of the measurementreporting obtained from terminal devices in accordance with theprinciples described herein when determining whether, and if so how, tooperate one or more secondary carriers supporting communications withone or more terminal devices in the unlicensed band—i.e. the basestation may take account of the measurement reports it receives toestablish operating characteristics for communications on the secondarycomponent carrier.

Thus, the LTE-A (primary) carrier provides a Pcell for the terminaldevices 406 and LTE-U resources support an Scell that may be configuredfor use by the terminal devices 406 and in respect of which the terminaldevices 406 are configured to provide measurement reports. It will beappreciated that radio resources in the second frequency band may beused to provide component carriers associated with multiple Scells inaccordance with conventional carrier aggregation techniques. It willalso be appreciated that while the present examples primarily focus onimplementations in which the LTE-A transmissions in the licencedfrequency band and the LAA transmissions in the shared frequency bandare made from the same base station 404, this need not be the case inother example implementations. Furthermore, it will be appreciated theLTE-U carrier could in general be utilised with a TDD (time divisionduplex) or FDD (frequency division duplex) frame structure.

One significant aspect of the approach represented in FIG. 5 inaccordance with certain embodiments is that one or more of the terminaldevices 406 may be configured for measurement and event reporting inrespect of radio resources within the second frequency band (i.e. radioresources which are, or may be, configured to support LAA operations onthe secondary carrier) even if the terminal device is operating in anRRC idle mode. That is to say, terminal devices may in accordance withcertain embodiments be configured to provide measurement reporting inrespect of radio resources associated with LAA operations supported by abase station even if the terminal devices are not themselves involved inthe LAA operations.

As is well understood, terminal devices in wireless telecommunicationssystems may be supported in different operating modes having regard tothe extent to which they are able to receive certain types of data, suchas user-plane data. For example, in an LTE-based network, such asrepresented in FIG. 4, there are two Radio Resource Control (RRC) modesfor terminal devices, namely: (i) RRC idle mode (RRC_IDLE); and (ii) RRCconnected mode (RRC_CONNECTED). To receive user-plane data, or at leasta certain type of user plane data, terminal devices must be in RRCconnected mode while terminal devices in RRC idle mode do not receivesuch data. In RRC idle mode, the core network (CN) part of the wirelesstelecommunications system recognizes the terminal device is presentwithin the system, but the radio access network (RAN) part of thewireless telecommunications system does not. In effect, in an RRC idlemode the terminal device is not connected to the base station. Theprocess of going from RRC idle mode to RRC connected mode may bereferred to as connecting to a cell/base station and the process ofgoing from RRC connected mode to RRC idle mode may be referred to asreleasing a connection to a cell.

FIG. 5 is a signalling ladder diagram schematically representing examplemodes of operation for the base station (eNB) 404 and the first terminaldevice 406 a (UEa), second terminal device 406 b (UEb) and thirdterminal device 406 c (UEc) represented in FIG. 4 in accordance withcertain embodiments of the present disclosure. To broadly summarise,FIG. 5 represents a measurement reporting approach for a wirelesstelecommunications system that supports a connected mode of operation inwhich terminal devices receive user-plane data from networkinfrastructure equipment, such as a base station, using a primary and/orsecondary component carrier and an idle mode of operation in whichterminal devices do not receive user-plane data from the networkinfrastructure equipment on the primary or secondary component carrier.In accordance with the principles disclosed herein, and describedfurther below, one or more terminal devices operating in the idle modeis configured to make a measurement of radio channel conditions forradio resources within the second frequency band in accordance with ameasurement configuration that is established for the measurement, andto then determine if the measurement meets a predefined triggercriterion (e.g. determining if more than a predefined threshold level ofradio interference is detected on the radio resources in respect ofwhich the measurement made). If so, the terminal device may transmit ameasurement report to the network infrastructure equipment to indicatethe trigger criterion has been met, thereby allowing the base station toconsider whether, and if so how, to modify any aspects of how itsupports LAA operations on the secondary carrier (for example in termsof whether the LAA carrier should be used, and if so, which radioresources within the unlicensed band should be used to support thesecondary carrier).

The processing represented in FIG. 5 starts from a point in which thefirst terminal device 406 a, UEa, is operating in the RRC connected mode(as schematically indicated step S1 a in FIG. 5) while the secondterminal device 406 b, UEb, and third terminal device 406 b, UEc, areoperating in the RRC idle mode (as schematically indicated in step S1 band S1 c in FIG. 5). Thus, the terminal devices UEb and UEc are notinvolved in receiving user-plane data from the base station 404 on theprimary or secondary component carriers associated with LAA operation.However, the terminal device UEa is assumed to be involved in ongoingcommunications with the base station and receiving data on the primarycomponent carrier and the secondary component carrier in accordance withthe principles of any known schemes for LAA operation (as schematicallyindicated step S2 a in FIG. 5). This situation may be assumed to havearisen in accordance with conventional operating procedures within thewireless telecommunications system, for example having regard to whetheror not the respective terminal devices have a need to communicateuser-plane data at the corresponding time. Although in this particularscenario the first terminal device UEa is assumed to be involved inongoing LAA communications and, as described herein, terminal devices inidle mode may be configured to provide measurement reporting to supportthe base station's LAA operation, the operating status of the firstterminal device in this regard is not significant to the process ofmeasurement reporting in accordance with the principles describedherein. For example, even when the base station is not supporting LAAoperations with the first terminal device UEa (or indeed with any otherterminal devices), measurement reporting in accordance with theprinciples described herein may still be employed to allow the basestation to determine an appropriate configuration for subsequent LAAoperation. For example, a wireless telecommunications system may beconfigured to employ measurement reporting in respect of radio resourcesin an LAA band using idle mode terminal devices as described herein todetermine whether or not LAA operations should be initiated, for examplein response to an increase in traffic load, even when LAA operation isnot currently configured for use.

As is well known, base stations in wireless telecommunications systemsbroadcast information that allows terminal devices to operate within thebase station's cell. In an LTE-based wireless telecommunications systemsome of the fundamental information required for a terminal device tooperate in a cell is transmitted on PBCH in the Master Information Block(MIB). Other information regarding the system configuration is dividedamong System Information Blocks (SIBs) referred to as SIB1, SIB2, SIB3,. . . etc. (there are 16 SIBs defined as of Release 11 LTE). The SIBsare transmitted in system information (SI) messages, which, apart fromSIB1, may contain multiple SIBs. There may be one or several SI messagestransmitted at different periodicities. Each SI message may conveymultiple SIBs suitable for scheduling with the same periodicity. Thetimings for SIB1 transmissions are fixed on an 80 ms period and theyoccur in the fifth subframe of radio frames when System Frame Number(SFN) is a multiple of 8 (i.e. SFN mod 8=0). There are retransmissionsof SIB1 provided in every other radio frame within the 80 ms period. Thetimings for other SIB transmissions are configured in SIB1. Thetransmission resource allocations for the SI messages on PDSCH within asubframe are provided to terminal devices using PDCCH allocationmessages addressed to SI-RNTI (System Information Radio NetworkTemporary Identifier—currently 0xFFFF in LTE). At higher layers, SI iscarried on the logical broadcast control channel (BCCH). Thus, systeminformation signalling provides an established mechanism for allowingbase stations to convey configuration information to terminal devices.

In accordance with embodiments of the disclosure, the base station 404is adapted to transmit system information which includes measurementconfiguration information defining how terminal devices should monitorradio channel conditions for radio resources within the second frequencyband, and this may be regardless of whether the terminal devices areoperating in the connected mode or the idle mode. In one implementation,the measurement configuration conveyed by the information in systeminformation may define one or more measurement objects which the basestation would like the terminal devices to monitor and report on if acorresponding trigger condition is met.

Thus, as represented in step S3 in FIG. 5, the base station transmitssystem information which comprises a LAA measurement configuration, forexample conveying information with regard to which radio resourcesshould be monitored by the terminal devices in accordance withembodiments of the disclosure and characteristics relating to thecriterion/criteria which, when met, give rise to a measurement report.For example, the measurement configuration may indicate the terminaldevices should measure radio channel conditions on radio resourcescorresponding to a frequency channel which the base station is currentlyusing for LAA operation in the second frequency band, for example tosupport communications with the first terminal device UEa as representedin step S2 a of FIG. 5. The measurement configuration may furtherindicate the nature of the measures to be made, for example whether themeasurement should comprise a measurement of a received power forreference signalling from the base station on the relevant radioresources, e.g. RSRP in an LTE context, and/or a measurement of areceived quality for reference symbol signalling on the relevant radioresources, e.g. RSRQ in an LTE context, and/or a measurement of areceived signal strength on the relevant radio resources, e.g. RSSI inan LTE context. In this regard, the measurements themselves may broadlycorrespond with conventional measurements made in wirelesstelecommunications systems. The measurement configuration may furtherprovide an indication of when the measurement should be made, forexample by defining a monitoring schedule for the measurements.

In steps S4 a, S4 b and S4 c represented in FIG. 5 the respectiveterminal devices UEa, UEb, UEc begin monitoring for an event triggercondition in accordance with the measurement configuration received instep S3. A significant aspect of this is that the terminal devices UEband UEc operating in the idle mode monitor for the event triggercondition in much the same way as the terminal device UEa operating inthe connected mode. Apart from this, the step of monitoring for theevent trigger condition may be based on generally established techniquesof the kind performed by RRC connected terminal devices in wirelesstelecommunications systems. For example, the respective terminal devicesmay each be configured to measure a characteristic of radio channelconditions on the relevant radio resources within the second frequencyband, for example in an LTE context this may be RSRP, RSRQ or RSSI, anddetermine whether or not their measurements indicate a predefinedcondition for triggering a measurement report is met. For example, theterminal devices may be configured to trigger a measurement report ifRSRP or RSRQ measurements fall outside a range defined by a thresholdvalue. More generally, the terminal devices may be configured to triggera measurement report if they determine that a level of interference onthe radio resources with which their current measurement configurationis associated is determined to exceed a predefined threshold(potentially also requiring this to occur for at least a certain amountof time—i.e. a “time-to-trigger”). In this regard, aspects of thetrigger conditions (e.g. threshold value and/or time-to-trigger) may beselected in accordance with established techniques for settingmeasurement report trigger conditions in wireless telecommunicationssystems. Characteristics defining the trigger condition may be specifiedin an operating standard for the wireless telecommunications systems ormay be selectable by the base station and conveyed to the terminaldevices in prior signalling, for example in conjunction with the LAAmeasurement configuration of step S3. It is assumed here the respectiveterminal devices are configured to monitor for the event triggercondition by making a measurement of the relevant radio channelconditions and determining if the measurement meets the pre-definedtrigger condition in a repeated manner in accordance with a monitoringschedule. For example, the terminal devices may be configured to performthe measurements on a regular basis.

In step S5 b represented in FIG. 5 it is assumed the second terminaldevice UEb determines that it has made a measurement of radio channelconditions that meets the condition for triggering a measurement report.This may be, for example, because the terminal device UEb is locatedrelatively near to a WLAN access point that has begun operating on radioresources and so increases the interference measured by the terminaldevice UEb (in principle this increased interference could be associatedwith activation of a Wi-Fi module of the second terminal device itself).It is assumed here the first terminal device UEa involved in LAAcommunications with the base station 404 does not see any increase ininterference because it is too far from the WLAN access point to receiveit signalling. Accordingly, and as already discussed above, this cangive rise to an issue with conventional measurement reporting approachesrestricted to RRC connected terminal devices because the terminal deviceUEa that is operating on the LAA resources is not aware of theinterference issue associated with the LAA operation. This means that inaccordance with existing schemes the base station might simply continuemaking LAA transmissions that interfere with the WLAN access point.However, in accordance with embodiments of the disclosure, the secondterminal device UEb which is currently in idle mode and not involved inany user-plane communications with the base station on the secondarycomponent carrier, is nonetheless made aware of the interference issueand may report this to the base station.

Having determined that a measurement report should be communicated tothe base station in Step S5 b, the second terminal device UEb proceedsto establish an RRC connection with the base station (as indicated inFIG. 5 in step S6 b) so that it becomes RRC connected (as indicated instep S7 b). This process of switching from idle mode to connected modemay be performed in accordance with any conventional techniques.

Having transitioned to connected mode, and as indicated in step S8 b inFIG. 5, the second terminal device UEb transmits a measurement report tothe base station to indicate the relevant trigger criterion has beenmet. The transmission of the measurement report may be made inaccordance with conventional measurement reporting techniques.

After transmitting the measurement report to the base station in step S8b terminal device UEb releases its RRC connection and returns to idlemode, as schematically represented in step S9 b in FIG. 5. This processof RRC connection release and switching from connected mode to idle modemay be performed in accordance with conventional techniques. Havingreturned to RRC idle mode, and as represented in Step S10 b, the secondterminal device UEb continues to monitor for the event triggercondition. This may be performed in the same way as described above withreference to step S4 b. In some example implementations the terminaldevice may be configured to delay transmitting any further measurementreports for a period of time after it has already done so. This may beto allow time for the base station to take action to seek to resolve theinterference issue. In some cases the terminal device may remain in RRCconnected mode for a period of time to allow it to more readily sendfurther measurement reports in respect of further measurements of radiochannel conditions so as to provide ongoing feedback to the base stationas to whether the issue has been resolved without needing to repeatedlyswitch between RRC connected mode and RRC idle mode.

Having received the measurement report in step S8 b, the base station404 proceeds to determine whether it should modify any aspects of itsLAA operation. For example, the base station may determine whether itshould cease LAA operation on the relevant radio resources, for exampleby switching the secondary component carrier to other radio resources,or deactivating the secondary carrier for a period of time to allow theWLAN access point to access the radio resources without interference (orat least with reduced interference) from the base station transmissions.This decision-making may in general be performed in accordance withconventional measurement report based decision-making techniques, and inparticular those proposed for use in LAA scenarios. That is to say, whatis significant in accordance with certain embodiments of the disclosureis the manner in which terminal devices in idle mode may be configuredto measure radio channel conditions on radio resources associated withLAA operation even though they are not involved in the LAA operation andnot how the measurement reports are handled. Once the base stationreceives the measurement report it may be handled in a conventionalmanner with regard to the base station determining whether, and if sohow, it should modify its LAA operation taking account of themeasurement report. In the example represented in FIG. 5, it is assumedthe base station 404 determines in step S9 that it should modify anoperating characteristic of its LAA operation I view of the measurementreport received from the second terminal device UEb. For example, thebase station may determine that it should modify one or morecharacteristics of the secondary component carrier being used to supportcommunications with the first terminal device UEa, such as the radioresources within the second frequency band used for the secondarycomponent carrier, or a determination that the secondary componentcarrier should be deactivated, or a determination that downlinkcommunications on the secondary carrier should not be scheduled for aperiod of time, e.g. as defined in accordance with establishedfairness/politeness protocols.

As schematically represented in FIG. 5 in step S5 a, after determiningthat it should modify an operating characteristic of its LAAcommunications in step S9, the base station communicates the modifiedLAA configuration information to the first terminal device UEa andcommences LAA operation in accordance with the modified LAAconfiguration (for example using different frequency resources withinthe second frequency band from those used for the LAA operation of stepS2 a). This aspect of the processing represented in FIG. 5 may beperformed in accordance with previously proposed techniques forsupporting changes in LAA operating characteristics in wirelesstelecommunications systems.

Thus, the processing described above with respect to the first andsecond terminal devices UEa, UEb show how a terminal device operating inan idle mode can be configured to provide measurement reports in respectradio resources supporting LAA operation for another terminal deviceoperating in a connected mode. In effect, this means that terminaldevices which are not involved in ongoing LAA operations can nonethelessprovide the base station with information regarding how the LAAtransmissions are interacting with transmissions for other wirelesscommunications devices associated with a different wireless accesstechnology (or a different telecommunications network operatingaccording to the same wireless access technology) within the same radioenvironment.

Another aspect of operations in accordance with certain embodiments ofthe disclosure will now be described with reference to the processingsteps associated with the first terminal device UEc represented in FIG.5.

As already discussed above, in step S4 c the terminal device UEc beginsmonitoring for the event trigger condition. It is assumed here the thirdterminal device UEc continues doing this without determining the triggercondition has occurred (e.g. because it is also too far from the WLANaccess point interfering with the measurements made by the secondterminal device as described above) until a point in time at which itwishes to establish RRC connection to the base station (as indicated inFIG. 5 in step S5 c) so that it becomes RRC connected (as indicated instep S6 c). This process of switching from idle mode to connected modemay be performed in accordance with conventional techniques and thereason why the switch is made is not significant here. For example, theswitch to connected mode may be made because the terminal device UEc hasdata it needs to transmit to the base station or because the basestation has paged the terminal device UEc.

After switching to RRC connected mode, the terminal device UEc continuesto monitor for the event trigger condition in accordance with the LAAmeasurement configuration received in step S3 while in the connectedmode. In this regard, a significant aspect of the processing representedin FIG. 5 is that a terminal device may continue monitoring for atrigger event in accordance with a LAA measurement configuration (e.g.defining one or more measurement objects) after switching from idle mostto connected mode. That is to say, a significant aspect of certainembodiments of the disclosure is in maintaining a measurementconfiguration after a change in RRC state (i.e. from idle to connectedor, as discussed further below, from connected to idle.)

When the base station modifies its LAA operation, it may be appropriateto reconfigure the measurements performed by terminal devices to suitthe modified LAA configuration (e.g. because there has been a change inradio resources used to support the LAA carrier). Such a change may beconveyed by updating system information to reflect the new configurationin accordance with conventional techniques. In this regard, it will beappreciated that for changes of system information other than thoserelated to EAB (Extended Access Barring), ETWS (Earthquake TsunamiWarning System) and CMAS (Commercial Mobile Alert System), there is aBCCH modification period defined (which may be referred to as a “SImodification period”). SI modification period boundaries are defined onradio frames for which SFN mod q=0, for a cell-specific value of q. Whenthere is a change in system information, the new system information istransmitted from the start of a new SI modification period.

The general process for implementing a change in system information inan LTE-based network is described, for example, in ETSI TS 136 331 V11.7.0 (2014-03)/3GPP TS 36.331 version 11.7.0 Release 11 [6]. Insummary, a base station indicates a change of system information asfollows.

1. When the network changes system information it notifies terminaldevices about the change by transmitting a PDCCH resource allocationmessage addressed to the paging RNTI (P-RNTI). This directs the terminaldevices to decode PDSCH resources containing a Paging message with aSystemInfoModification flag set to true. This may be done, for example,throughout one SI modification period. Both RRC_IDLE and RRC_CONNECTEDterminal devices check for paging messages periodically. It may be notedthat EAB alterations, ETWS and CMAS notifications may be separatelymodified with separate flags in a paging message (but can also bemodified along with other SIBs).

2. In a following SI modification period, the network transmits themodified system information, and may increment a SystemInfoValueTag inSIB1. This value tag can indicate changes in any SIB, but it might notbe used for EAB, ETWS, CMAS and some regularly changing SI parameterssuch as CDMA2000 system time. Terminal devices can useSystemInfoValueTag to verify if currently stored system information isstill valid, for example on return from being out of coverage when theUE may have missed a system information change notification in paging.

The terminal devices may thus be advised of the need to acquire newsystem information reflecting a change in LAA configuration insignalling received from the base station. This may be performed inaccordance with conventional techniques. For example in the same way asexisting schemes associated with non-EAB, non-ETWS, and non-CMAS systeminformation update approaches, or where a faster response is desired,using existing schemes based on EAB, ETWS, CMAS system informationupdate approaches.

More details on system information and changes in system information inan LTE-based system can be found in ETSI TS 136 331 V 11.7.0(2014-03)/3GPP TS 36.331 version 11.7.0 Release 11 [6].

As noted above, in some implementations, a base station mayalternatively, or in addition, convey LAA measurement configurationinformation to individual terminal devices through dedicated signalling,and an example of this is schematically represented in step S8 c whichshows the base station conveying an updated LAA measurementconfiguration to the first terminal device (in practice it may beexpected the base station will also convey the indication of the updatedLAA measurement configuration to the other terminal devices, e.g.through updated system information or dedicated signalling correspondingto that represented step S8 c, but this is not shown in FIG. 5 forsimplicity).

As schematically represented in step S9 c, the terminal device UEcreceiving the updated LAA measurement configuration proceeds to monitorfor the event trigger condition in accordance with the updatedmeasurement configuration (as will other terminal devices receiving theupdated measurement configuration, whether in idle mode or connectedmode). Apart from the different measurement configuration (e.g.different radio resources and/or different trigger criterion) theterminal device UEc may monitor for the updated event trigger conditionin the same manner as described above (albeit with the terminal devicecurrently in RRC connected mode).

It is assumed here this third terminal device UEc continues doing thiswithout determining the updated trigger condition has occurred until apoint in time at which it releases its RRC connection and returns to RRCidle mode, as schematically indicated in FIG. 5 in step S10 c. Thisprocess of switching from connected mode to idle mode may be performedin accordance with conventional techniques and the reason why the switchis made is not significant here. For example, the switch to idle modemay be made because the terminal device UEc.

After switching to RRC idle mode, the terminal device UEc continues tomonitor for the event trigger condition in accordance with the updatedLAA measurement configuration received in step S8 c while in the idlemode, as schematically represented in step S11 c. In this regard, and asalready noted, a significant aspect of the processing represented inFIG. 5 is that a terminal device may continue monitoring for a triggerevent in accordance with a current LAA measurement configuration afterswitching from connected mode to idle mode (i.e. an RRC statetransition). In this regard a terminal device may thus performmeasurements in accordance with a measurement configuration received bythe terminal device when in a connected mode after it has switched to anidle mode. Conversely, a terminal device may perform measurements inaccordance with a measurement configuration received by the terminaldevice when in an idle mode after it has switched to a connected mode.

Although not shown in FIG. 5, if a terminal device determines from ameasurement of the relevant radio channel conditions that the criterionfor triggering a measurement report is met when the terminal devicehappens to be operating in RRC connected mode, the terminal device mayproceed to transmit a measurement report to the base station to indicatethis has happened in accordance with conventional measurement reportingtechniques.

It will be appreciated there are various aspects of the processingrepresented in FIG. 5 that may be different for other implementations ofembodiments of the disclosure. For example, rather than have themeasurement configuration information conveyed by the base station tothe terminal devices in system information, other techniques may beadopted. For example, the LAA measurement configuration may becommunicated to individual terminal devices through dedicatedsignalling.

Furthermore, whereas the description of the processing represented inFIG. 5 has primarily focused on a situation in which the triggercondition is associated with determining a level of interferencemeasured in respect of the relevant radio resources exceeds a thresholdamount, in another example the trigger condition may be associated witha terminal device determining that the secondary component carrier isconfigured for use on radio resources which are known by the terminaldevice to be in use by another radio access technology. This may be, forexample, because the terminal device itself wishes to use the relevantradio resources for communicating in accordance with another radioaccess technology (e.g. Wi-Fi or Bluetooth), or because the terminaldevice recognises that another wireless communications device is alreadyusing those resources, for example from Wi-Fi channel configurationinformation being transmitted in association with the other wirelesscommunications device. In this regard, determining whether the triggercriterion is met may comprise determining if the base station istransmitting on radio resources which overlap with radio resources beingused by another wireless communications device operating within acoverage area of the base station. That is to say, in accordance withthe terminology used herein the process of making a measurement of radiochannel conditions in accordance with a measurement configuration shouldbe interpreted broadly to include determining if a measurementconfiguration is associated with radio resources which are known to bein use by another radio access technology without necessarily requiringany actual physical channel measurements to be made. In this regardmaking a measurement of radio channel conditions in accordance with theprinciples described herein may also be referred to as assessing radiochannel conditions.

In some implementations, there may be some aspects of measurementconfiguration which are automatically modified on transition betweenidle and connected mode. For example, in idle mode a terminal device maybe configured to trigger measurement of supporting only if its own WLANmodule starts a communication session on radio resources correspondingto the LAA channel configured for measurement, whereas in connected modethe terminal device may automatically become configured to triggermeasurement reporting based upon detection of an interference levelbeing above a threshold.

Thus the approaches described above with reference to FIG. 5 representnew ways of providing measurement reports in wireless telecommunicationssystems supporting LAA operation. These approaches show how any terminaldevice, even those not currently configured to use LAA, operating in awireless telecommunications system can be utilized to perform radiochannel measurements in real-time and to report if it is observinginterference issues. This can help address the hidden node problemdiscussed above by in effect providing the base station with moremeasurements of radio channel conditions. Furthermore, these approachescan be adopted in some implementations without significant overheadsignalling because only terminal devices which observe an interferenceissue may be configured to report corresponding measurements.Furthermore, in some implementations the measurement configuration maybe communicated by broadcast signalling (i.e. signalling transmitted toa plurality of terminal device), thereby avoiding the need toindividually configure terminal devices (although in someimplementations this may be done).

FIG. 6 is a signalling ladder diagram schematically representing examplemodes of operation for the base station (eNB) 404 and the first terminaldevice 406 a (UEa), second terminal device 406 b (UEb) and thirdterminal device 406 c (UEc) represented in FIG. 4 in accordance withcertain embodiments of the present disclosure. As with FIG. 5, thegeneral scenario represented in FIG. 6 is one in which the wirelesstelecommunications system 400 is configured to support LAA (LTE-U)operations based on previously proposed schemes with modifications toprovide functionality in accordance with embodiments of the disclosuredescribed herein. In particular, in accordance with certainimplementations, terminal devices (whether in idle or connected mode)may be requested to perform measurements (and corresponding measurementreporting based on the measurements as appropriate) in respect of radioresources in the second frequency band which are being used (or may beused) for LAA operation. The base station may then take account of themeasurement reporting obtained from terminal devices in accordance withthe principles described herein when determining whether, and if so how,to operate one or more secondary carriers supporting communications withone or more terminal devices in the unlicensed band—i.e. the basestation may take account of the measurement reports it receives toestablish operating characteristics for communications on the secondarycomponent carrier.

The measurements may be requested (triggered) by the base stationtransmitting a request message to a plurality of terminal devices torequest that at least some of the plurality of terminal devices makemeasurements of radio channel conditions for radio resources within thesecond frequency band in accordance with a measurement configurationassociated with the request message. The request message may, forexample, comprise group paging addressed to (i.e. comprising anidentifier associated with) a plurality of terminal devices.

The request message may comprise measurement configuration informationfor the measurement to be made. In some examples this may comprise anindication of specific measurement configuration parameters (for examplein terms which radio resources to measure and/or when to measure and/orwhat radio channel condition to measure and/or a measurement reporttrigger condition). In other examples the measurement configurationinformation may comprise an indication of a previouslyestablished/semi-static measurement configuration to use, for example byreference to an identifier for one or more predefined potentialmeasurement configurations. For this approach the predefined potentialmeasurement configurations may, for example, be defined by systeminformation signalling transmitted by the base station in advance of therequest message, or may be defined in accordance with an operatingspecification for the wireless telecommunications system. In yet otherexamples the system may be associated with a single measurementconfiguration for the terminal devices to use when they receive arequest to make measurements. In this case the request message may notcomprise any express indication of the measurement configuration to useand the terminal devices may simply use whichever measurementconfiguration is currently defined, for example based on previouslyreceived measurement configuration information or measurementconfiguration information defined in accordance with an operatingstandard for the wireless telecommunications system. For the exampleimplementation represented in FIG. 6, and as described further below, itis assumed a plurality of potential LAA measurement configurations arecommunicated to terminal devices in system information and a subsequentrequest message indicates which of these plurality of potentialmeasurement configurations are to be used for the correspondingmeasurements.

On receiving a measurement report from one or more terminal devices inaccordance with the principles described herein, the base station maytake account of the measurement report(s) when determining whether, andif so how, to operate one or more secondary carriers supportingcommunications with one or more terminal devices in the unlicensedband—i.e. the base station may take account of the measurement reportsit receives to establish operating characteristics for communications onthe secondary component carrier. In this regard the base station mayrespond to the measurement reports in much the same way as describedabove for the processing represented in FIG. 5.

The processing schematically represented in FIG. 6 starts with thetransmission of system information from the base station 404 which isreceived by the respective terminal devices 406 a, 406 b and 406 c asschematically indicated in step T1. The system information may bereceived by the terminal devices in accordance with conventionaltechniques. However, the system information is modified to includeinformation relating to a plurality of potential LAA measurementconfigurations. The different potential measurement configurations may,for example, correspond with different potential LAA channelconfigurations that may be supported by the base station. For example,there may be a number of potential LAA configurations that the basestation may adopt, and with different LAA configurations may beassociated with different radio resources within the second frequencyband being used for the secondary component carrier. In this case theremay be a corresponding number of potential measurement configurationsestablished, with each potential measurement configuration providing ameasurement in respect of the radio resources associated with acorresponding one of the potential LAA configurations. In someimplementations, different measurement configurations may additionallyor alternatively provide different threshold levels or criteria fortriggering a measurement report, different valuation periods(times-to-trigger) or different reporting quantities/parameters (e.g.from among RSRP, RSRQ, RSSI). It will be appreciated there are otherways in which the base station may communicate the relevant LAAmeasurement configuration information to the terminal devices. Forexample, instead of, or in addition to, using system information thepotential measurement configurations may be associated with respectivemeasurement objects configured for the respective terminal devicesthrough radio resource control signalling transmitted by the networkinfrastructure equipment to the respective terminal devices when inconnected mode.

The measurement configuration(s) may broadly correspond with thosediscussed above. For example, the movement configuration(s) may compriseinformation with regard to which radio resources should be measured bythe terminal devices and the nature of the measurements to be made (forexample whether the measurement should comprise a measurement of areceived power for reference signalling from the base station on therelevant radio resources and/or a measurement of a received power forreference symbol signalling on the relevant radio resources and/or ameasurement of a received signal strength on the relevant radioresources (e.g. if there are no reference symbols being transmitted onthe relevant radio resources, for example because the secondarycomponent carrier is not currently activated on those resources)).

In step T2 the base station decides to establish radio channel conditionmeasurements in accordance with one (or more) of the measurementconfigurations defined by the signalling of Step T1. The exact reasonwhy the base station wishes to establish these measurements is notsignificant. For example, it may be that the base station is currentlysupporting a secondary component carrier on particular radio resourceswithin the second frequency band, and wishes to obtain an overview ofthe radio channel conditions associated with the secondary carrier seenby various terminal devices operating in the wireless telecommunicationsnetwork within the base station's coverage area. This may be because thebase station is considering modifying its current LAA operation, forexample in response to changing data traffic requirements, or simplybecause the base station is configured to request measurements on aregular basis as part of an ongoing monitoring process. In anotherexample, the base station might not currently be operating a secondarycomponent carrier on particular radio resources within the secondfrequency band, but may wish to determine if it is able to startoperating a secondary carrier on these resources without undulyinterfering with ongoing communications associated with other radioaccess technologies or another operator's wireless telecommunicationsnetwork operating in the shared band in the radio environment of thebase station.

Thus, in step T3 the base station transmits a request message to aplurality of terminal devices to request that the plurality of terminaldevices make measurements of radio channel conditions for radioresources within the second frequency band in accordance with ameasurement configuration associated with the request message andprovide a corresponding measurement report to the base station. In thisrespect, one significant aspect of certain embodiments of the disclosureis that a base station may ask multiple terminal devices operating inthe wireless telecommunications system for a measurement report. Therequest message may be transmitted in the form of a paging messageaddressed to those terminal devices which the base station would like toperform measurement reporting. In principle this could be every terminaldevice operating in the cell of the base station, or at least thosehaving the capability of making measurements within the second frequencyband, but in other cases the request message may be addressed only to asubset of the terminal devices. For example, the base station couldaddress the paging message to a selected number of terminal deviceswhich are explicitly identified in the paging message. Alternatively, asingle group paging identity could be used which is associated with aplurality of terminal devices. Membership of the group could beestablished in prior signalling, for example terminal devices may beprovided with an indication of one or more paging group identities withwhich they are associated during an earlier connection to the network.Membership of a paging group could also be established based onidentifiers already associated with the terminal device, such as an IMSIor IMEI. For example, in order to request that 10% (statistically) ofterminal devices react to a paging message, the paging message mayindicate that any terminal devices associated with an IMSI/IMEI (orother identifier) ending in a specific single digit provided in thepaging message should respond. Similar approaches can be used to requestresponses from different proportions of terminal devices. For example,if the base station would like one in eight terminal devices to respond,the paging message may indicate that any terminal devices having noremainder when dividing their identifier by eight should respond.Another approach to establishing which of the terminal devices shouldrespond would be to provide an indication of the specific terminaldevices (for example by reference to their IMSI/IMEI or otheridentifier) in system information broadcast by the base station.Terminal devices receiving the paging message may thus be configured toacquire this aspect of system information to see if they should react tothe paging message. Yet another way to address a paging message to onlya certain subset of terminal devices would be to send the paging messagein only some paging occasions (paging occasions are a function ofterminal device identity). In some situations the base station may beinterested in responses from one or more specific terminal devices (forexample because of an aspect of their previous measurement reporting ortheir location within the cell) and may target the paging requestaccordingly, whereas in other cases the subset of terminal devices mayin effect be established randomly by the base station.

The request message further includes an indication of which of theplurality of potential LAA measurement configurations previouslyconveyed to the terminal devices in step T1 are to be used for themeasurement in respect of which the request is made. For example, therequest message may include a reference/index/identifier which indicatesthe relevant LAA measurement configuration which the base station wouldlike the terminal devices to use. Accordingly, terminal devicesreceiving the request message are able to determine the nature of themeasurement they are being requested to make (e.g. in terms of the radioresources in the second frequency band for which channel conditions areto be measured) from the request message.

In steps T4 a, T4 b and T4 c represented in FIG. 6 the respectiveterminal devices UEa, UEb, UEc perform the requested measurement inaccordance with the relevant measurement configuration. In this regardthe measurements themselves may be based on generally establishedtechniques for radio channel condition measurement and measurementreporting in wireless telecommunications systems. Thus, the respectiveterminal devices may each measure a characteristic of radio channelconditions on the relevant radio resources within the second frequencyband, which may, for example in an LTE context, be RSRP, RSRQ or RSSIdepending on the specific measurement configuration. This measurementmay be performed by terminal devices regardless of whether or not theyare in idle or connected mode when they receive the request message. Aterminal device operating in idle mode when it receives the requestmessage may transition to connected mode before making the measurement,or may make the measurement in idle mode, and then transition to theconnected mode to make a measurement report (to the extent a measurementreport is to be transmitted by that terminal device, for example havingregard to whether its measurement meets a measurement report triggercondition). The measurements undertaken by the terminal devices may alsobe associated with a validity time. For example the terminal device maymake measurements to monitor for the trigger condition, and determine ifthe trigger condition is not met within a specified period, it may ceasemaking measurements.

In steps T5 a, T5 b and T5 c represented in FIG. 6 the respectiveterminal devices UEa, UEb, UEc transmit measurement reports to the basestation indicating the results of their respective measurements of radiochannel conditions in accordance with the measurement request receivedin step T3. Any terminal devices making their measurement in idle modemay transition to RRC connected mode before doing this, for example inthe manner described above with reference to the measurement reportingapproach represented in FIG. 5. The transmission of the measurementreports from the respective terminal devices to the base station may bemade in accordance with conventional measurement reporting techniques.

As schematically indicated in step T6, and having received themeasurement reports in steps T5 a, T5 b and T5 c, the base station 404proceeds to determine whether it should modify any aspects of its LAAoperation, i.e. modify any operating characteristic(s) for the secondarycomponent carrier based on the measurement reports. For example, if themeasurement reports indicate an undesirable degree of radio interferenceis observed by one or more terminal devices on the measured radioresources in the second frequency band, the base station may determineit should cease LAA operation on the relevant radio resources, forexample by switching the secondary component carrier to other radioresources, or deactivating the secondary carrier for a period of time.As with the processing represented in FIG. 5, this decision-making mayin general be performed in accordance with conventional measurementreport based decision-making techniques, and in particular those thathave been proposed for LAA scenarios. That is to say, what issignificant in accordance with certain embodiments of the disclosure isthe manner in which a plurality of terminal devices may be requested tomake measurements of radio channel conditions for radio resources withinthe second frequency band in accordance with a measurement configurationassociated with a request message rather than how the measurementreports are handled. Accordingly, once the base station receives themeasurement reports they may be handled in a conventional manner withregard to the base station determining whether, and if so how, it shouldmodify its LAA operation taking account of the measurement reports. Ifbased on the measurement reports the base station determines that itshould modify an aspect of its LAA operations, it may proceed to do soaccordingly. This aspect of the processing may be performed in anyconventional manner and is not represented in FIG. 6.

Thus, the processing represented in FIG. 6 in steps T1 to T6 provides amechanism for a base station to readily ask a plurality of terminaldevices for measurement reports in respect of radio channel conditionsfor radio resources within the second frequency band based on ameasurement configuration associated with the request message. This canallow the base station to obtain information regarding radio channelconditions within its coverage area when determining an operatingcharacteristic of its LAA operation. For example, the measurementreports may be used when determining one or more operatingcharacteristics such as a selection of radio resources within the secondfrequency band to be used for the secondary component carrier, adetermination as to whether or not the secondary component carriershould be activated for use, and a determination as to whether or notthe secondary component carrier should be deactivated.

If the base station wishes to establish radio resource measurements fordifferent LAA resources corresponding to another of the predefinedpotential measurement configurations established in the signalling ofstep T1, the base station may simply send a request message similar tothat described above in association with step T3, but indicating thedifferent measurement configuration to be used.

However, there may be some situations where the base station determinesthat it wishes is to establish radio channel conditions for LAAresources which do not correspond with one of the currently-definedpotential measurement configurations. In this context, another aspect ofoperations in accordance with certain embodiments of the disclosure willnow be described with reference to the processing steps T7 to T12represented in FIG. 6.

Thus in step T7 the base station determines that it should establishradio channel condition measurements in respect of radio resources whichdo not correspond with one of the potential measurement configurationsestablished in association with step T1. As discussed above in relationto step T2, the exact reason why the base station wishes to establishthese measurements is not significant.

In order to convey the new LAA measurement configuration information tothe terminal devices the base station may update the system informationbeing transmitted in the cell to reflect the new LAA measurementconfiguration. Accordingly, in step T8 the base station pages theterminal devices to indicate they should acquire updated systeminformation. In this regard, the process of indicating the terminaldevices should acquire updated system information may be performed inaccordance with conventional techniques, such as discussed above, forexample using the existing schemes associated with non-EAB, non-ETWS,and non-CMAS system information update approaches, or where a fasterresponse is desired, using existing schemes based on EAB, ETWS, CMASsystem information update approaches.

Having indicated to the terminal devices that they should acquire theupdated system information, the base station transmits the updatedsystem information, as schematically indicated in step T9. Step T9 maybe performed in the same way as step T1 discussed above, except theinformation content of the system information signalling will reflectthe different measurement configuration information (e.g. specifying anew potential LAA measurement configuration associated with a new set ofradio resources to measure).

As schematically indicated in step T10, and after having provided theterminal devices with the updated measurement configuration informationin step T9, the base station transmits a request message to theplurality of terminal devices to request they make measurements of radiochannel conditions for radio resources within the second frequency bandin accordance with the newly established measurement configuration. StepT10 may be performed in the same manner as step T3 described above withthe request message (paging message) comprising an indication of therelevant one of the potential measurement configurations defined in thesystem information of step T9.

In a variation of the approach represented in FIG. 6, terminal devicesmay be configured to assume that whenever they acquire updated systeminformation with different LAA measurement configuration information(such as in step T9 presented in FIG. 6) they should also interpret thisas a request message to undertake a measure reporting process inaccordance with the principles described herein. That is to say, in someimplementations the signalling of step T10 may in effect be implicitsignalling and not comprise any explicit transmissions from the basestation.

In steps T11 a, T11 b and T11 c represented in FIG. 6 the respectiveterminal devices UEa, UEb, UEc perform the requested measurement inaccordance with the relevant measurement configuration. These steps maybe performed in the same manner as steps T4 a, T4 b and T4 c discussedabove.

In steps T12 a, T12 b and T12 c represented in FIG. 6 the respectiveterminal devices UEa, UEb, UEc transmit measurement reports to the basestation indicating the results of their respective measurements of radiochannel conditions in accordance with the measurement request receivedin step T10. These steps may be performed in the same manner as steps T5a, T5 b and T5 c discussed above.

Having received the measurement reports in steps T12 a, T12 b and T12 c,the base station 404 may proceed to determine whether it should modifyany aspects of its LAA operation in the same manner as discussed abovewith reference to step T6.

Accordingly, the processing of FIG. 6 demonstrates how a plurality ofterminal devices can be paged to provide measurement reports in respectof selected ones of different potential measurement configurations, andhow the potential measurement configurations may be changed.

It will be appreciated the processing represented in FIG. 6 may bemodified in accordance with other example implementations. For example,in the processing of FIG. 6 it is assumed that all terminal deviceswhich receive a request to make measurements send a measurement reportto the base station in respect of their measurements. However, in otherimplementation only a subset of the terminal devices receiving themeasurement request may send a report.

For example, in some implementations the respective terminal devices mayonly send a measurement report if their respective measurements meet atrigger condition, for example of the type discussed above with regardsto the approach of FIG. 5. For example, the terminal devices may beconfigured to only trigger a measurement report if they determine that alevel of interference on the radio resources they are requested tomeasure is determined to exceed a predefined threshold (potentially alsorequiring this to occur for at least a certain amount of time—i.e. a“time-to-trigger”). In this regard, and as already mentioned above inrelation to the FIG. 5 approach, aspects of the trigger conditions (e.g.threshold value and/or time-to-trigger) may be selected in accordancewith established techniques for setting measurement report triggerconditions in wireless telecommunications systems. Characteristicsdefining the trigger condition may be specified in an operating standardfor the wireless telecommunications systems or may be selectable by thebase station and conveyed to the terminal devices, for example inassociation with the request message. In cases where the terminaldevices may be configured to selectively respond to the request formeasurement based on the results of the measurement, this may always bethe case, or the request message may provide an indication that thisapproach is to be adopted in respect of a specific request.

Furthermore in some implementations only a subset of terminal devices towhich the request message is addressed may be expected to respond bymaking measurements. This is to help reduce the risk of large numbers ofmeasurement reports being transmitted at around the same time fromimpacting the performance of the wireless telecommunications system.

In cases where only a subset of the terminal devices to which therequest message is addressed are requested to undertake measurementreporting in accordance with the principles described herein, therequest message may comprise information indicating this is the case.For example, the request message may comprise an indication that a givenpercentage of terminal devices are requested to undertake measurementreporting. The terminal devices may then individually decide whether ornot to undertake measurement reporting on a statistical basis inaccordance with the desired percentage of respondents. For example, therequest message might indicate the base station would like only 10% ofterminal devices receiving the message to respond by undertakingmeasurements/measurement reporting. The terminal devices receiving therequest message may thus generate a random number between 0 and 1, anddetermine that they should proceed with measurement reporting only iftheir random number is between 0 and 0.1. Of course it will beappreciated there are many other ways in which the number of responsescan be restricted in this sort of way. For example, each terminal deviceoperating in a wireless telecommunications system will typically beassociated with some form of identifier, such as an IMSI, and therequest message may indicate a two-digit number, or multiple two-digitnumbers such as a range of numbers, whereby only terminal devices whoseidentifier comprises two digits at the end that match the number(s)identified in the request message will response to the request.

In some cases the subset of terminal devices which respond to therequest message may be based on their locations. For example, it iscommonplace for terminal devices to have an understanding of theircurrent geographic location, e.g. using GPS receiver technology.Accordingly, the base station may transmit a request message thatindicates only terminal devices within a certain region are requested torespond. This can help the base station understand the geographiclocation of areas of interference within its coverage area, for exampleto help identify the location of a “hidden node”. In another example,the base station itself may have knowledge of the locations of terminaldevices and may address the request message only to those in a desiredgeographic location. In another approach, the terminal device reportsmay themselves contain location information for the reporting terminaldevice to again help the base station map where interference isoccurring within its coverage area.

It will be appreciated there are various modifications of the processingrepresented in FIG. 6 that may be adopted in accordance with otherexample implementations. For example, rather than establish a pluralityof potential measurement configurations with the request messageindicating which measurement configuration is to be used, the requestmessage may itself comprise the information defining the measurementconfiguration to be used. This provides the base station with a higherdegree of flexibility in which measurements can be configured butincreases the amount of signalling required for the request message.

It will be appreciated that while the above-described embodiments arefocused on a single base station supporting both the primary componentcarrier the secondary component carrier, more generally these could betransmitted from separate base stations. In this regard, thenetwork-side processing in accordance with embodiments of the presentdisclosure may be performed by network infrastructure equipment whichcomprises, for example, one base station or more than one base station,and potentially other network infrastructure equipment elementsaccording to the operating principles of the wireless telecommunicationsnetwork in which the approach is implemented.

It will be appreciated the principles described above may be applied inrespect of a wireless telecommunications system supporting carrieraggregation with secondary component carriers operating in a frequencyband over which the wireless telecommunications system does not haveexclusive control irrespective of whether or not the wirelesstelecommunications system requires an administrative license to operatein the secondary frequency band. That is to say, it will be appreciatedthe terminology “unlicensed” is used herein for convenience to refer tooperation in a band over which the wireless telecommunications systemdoes not have exclusive access. In many implementations this willcorrespond with a licence exempt frequency band. However, in otherimplementations the operation may be applied in a frequency band whichis not unlicensed in the strict administrative sense, but which isnonetheless available for shared/opportunistic use by devices operatingaccording to different wireless access technologies (e.g. LTE-based,Wi-Fi-based and/or Bluetooth-based technologies) and/or multiplenetworks operating according to the same technology (e.g. LTE-basedwireless communication systems provided by different network operators).In this regard the terminology such as “unlicensed frequency band” maybe considered to refer generally to a frequency band in which resourcesare shared by different wireless communications systems. Accordingly,while the term “unlicensed” is commonly used to refer to these types offrequency bands, in some deployment scenarios an operator of a wirelesstelecommunications system may nonetheless be required to hold anadministrative license to operate in these frequency bands. Operation ofthe kind described herein is sometimes referred to as being LicenceAssisted Access (LAA) as opposed to being unlicensed. For example, theterm LTE-LAA may be used in place of LTE-U, and so on. This terminologyreflects the nature of the operation in using communications onfrequencies which are licensed for use by an operator to assist accesson other frequencies which are not exclusively licensed for use by theoperator.

Thus there has been described a method of operating a terminal device ina wireless telecommunications system. The system is configured tosupport communications between network infrastructure equipment andterminal devices using a primary component carrier operating on radioresources within a first frequency band and a secondary componentcarrier operating on radio resources within a second frequency band. Thesystem supports a connected mode of operation in which terminal devicesreceive a type user-plane data from the network infrastructure equipmentusing the primary and/or secondary component carrier and an idle mode ofoperation in which terminal devices do not receive that type ofuser-plane data from the network infrastructure equipment. The methodcomprises: establishing a measurement configuration for makingmeasurements of radio channel conditions for radio resources within thesecond frequency band; making a measurement of radio channel conditionsfor radio resources within the second frequency band in accordance withthe measurement configuration while the terminal device is operating inthe idle mode; determining if the measurement of radio channelconditions meets a trigger criterion, and if so, transmitting ameasurement report to the network infrastructure equipment to indicatethe trigger criterion has been met.

There has also been described a method of operating networkinfrastructure equipment in a wireless telecommunications system. thesystem is configured to support communications between the networkinfrastructure equipment and terminal devices using a primary componentcarrier operating on radio resources within a first frequency band and asecondary component carrier operating on radio resources within a secondfrequency band. The method comprises: transmitting a request message toa plurality of terminal devices to request that at least some of theplurality of terminal devices make measurements of radio channelconditions for radio resources within the second frequency band inaccordance with a measurement configuration associated with the requestmessage; receiving measurement reports from at least some of theplurality of terminal devices indicating their respective measurementsof radio channel conditions; and establishing an operatingcharacteristic for the secondary component carrier based on themeasurement reports.

Further particular and preferred aspects of the present invention areset out in the accompanying independent and dependent claims. It will beappreciated that features of the dependent claims may be combined withfeatures of the independent claims in combinations other than thoseexplicitly set out in the claims.

Thus, the foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. As will be understood by thoseskilled in the art, the present invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Accordingly, the disclosure of the presentinvention is intended to be illustrative, but not limiting of the scopeof the invention, as well as other claims. The disclosure, including anyreadily discernible variants of the teachings herein, define, in part,the scope of the foregoing claim terminology such that no inventivesubject matter is dedicated to the public.

Respective features of the present disclosure are defined by thefollowing numbered paragraphs:

Paragraph 1. A method of operating a terminal device in a wirelesstelecommunications system configured to support communications betweennetwork infrastructure equipment and terminal devices using a primarycomponent carrier operating on radio resources within a first frequencyband and a secondary component carrier operating on radio resourceswithin a second frequency band, wherein the wireless telecommunicationssystem supports a connected mode of operation in which terminal devicesreceive user-plane data from the network infrastructure equipment usingthe primary and/or secondary component carrier and an idle mode ofoperation in which terminal devices do not receive user-plane data fromthe network infrastructure equipment, wherein the method comprises:establishing a measurement configuration for making measurements ofradio channel conditions for radio resources within the second frequencyband; making a measurement of radio channel conditions for radioresources within the second frequency band in accordance with themeasurement configuration while the terminal device is operating in theidle mode; determining if the measurement of radio channel conditionsmeets a trigger criterion, and if so, transmitting a measurement reportto the network infrastructure equipment to indicate the triggercriterion has been met.

Paragraph 2. The method of paragraph 1, wherein the measurementconfiguration is established from signalling received from the networkinfrastructure equipment.

Paragraph 3. The method of paragraph 2, wherein the measurementconfiguration is established from system information signallingbroadcast by the network infrastructure equipment to a plurality ofterminal devices.

Paragraph 4. The method of paragraph 2, wherein the measurementconfiguration is established from dedicated signalling transmitted fromthe network infrastructure equipment to the terminal device.

Paragraph 5. The method of any one of paragraphs 1 to 4, furthercomprising the terminal device switching from the idle mode of operationto the connected mode of operation to transmit the measurement report tothe network infrastructure equipment.

Paragraph 6. The method of any one of paragraphs 1 to 5, wherein themeasurement configuration is associated with one or more measurementobjects specifying the radio resources within the second frequency bandin respect of which the measurement of radio channel conditions is to bemade.

Paragraph 7. The method of any one of paragraphs 1 to 6, wherein theradio resources in respect of which the measurement of radio channelconditions is made are associated with one or more frequency channels onwhich the secondary component carrier may operate in the secondfrequency band.

Paragraph 8. The method of any one of paragraphs 1 to 7, wherein themeasurement of radio channel conditions comprises one or moremeasurements selected from the group comprising: (i) a measurement of areceived power for reference signals transmitted by the networkinfrastructure equipment on the secondary component carrier; (ii) ameasurement of a received quality for reference signals transmitted bythe network infrastructure equipment on the secondary component carrier;and (iii) a measurement of a signal strength received by the respectiveterminal devices on the radio resources.

Paragraph 9. The method of any one of paragraphs 1 to 8, whereindetermining if the measurement of radio channel conditions meets thetrigger criterion comprises determining if a level of radio interferencedetermined from the measurement of radio channel conditions exceeds apredefined threshold value.

Paragraph 10. The method of any one of paragraphs 1 to 9, whereindetermining if the measurement of radio channel conditions meets thetrigger criterion comprises determining if the network infrastructureequipment is transmitting on radio resources which overlap with radioresources being used by a wireless communications device operatingwithin a coverage area of radio transmissions from the networkinfrastructure equipment.

Paragraph 11. The method of paragraph 10, wherein the wirelesscommunications device is the terminal device itself.

Paragraph 12. The method of any one of paragraphs 1 to 11, wherein themeasurement configuration comprises one or more indications selectedfrom the group comprising: (i) an indication of the radio resources inrespect of which the measurement of radio channel conditions is to bemade; (ii) an indication of when the measurement of radio channelconditions is to be made; (iii) an indication of how the measurement ofradio channel conditions is to be made; and (iv) an indication of thetrigger criterion.

Paragraph 13. The method of any one of paragraphs 1 to 12, furthercomprising the terminal device switching from the connected mode ofoperation to the idle mode of operation after establishing themeasurement configuration for making measurements of radio channelconditions and before making the measurement of radio channel conditionswhile the terminal device is operating in the idle mode.

Paragraph 14. The method of any one of paragraphs 1 to 13, furthercomprising the terminal device switching from the idle mode of operationto the connected mode of operation after making the measurement of radiochannel conditions while the terminal device is operating in the idlemode and making one or more measurements of radio channel conditions forradio resources within the second frequency band in accordance with themeasurement configuration while the terminal device is operating in theconnected mode.

Paragraph 15. The method of any one of paragraphs 1 to 14, furthercomprising the terminal device establishing an updated measurementconfiguration for making measurements of radio channel conditions forradio resources within the second frequency band; making a furthermeasurement of radio channel conditions for radio resources within thesecond frequency band in accordance with the updated measurementconfiguration; determining if the further measurement of radio channelconditions meets a trigger criterion associated with the updatedmeasurement configuration, and if so, transmitting a measurement reportto the network infrastructure equipment to indicate this.

Paragraph 16. The method of paragraph 15, wherein the updatedmeasurement configuration is established in response to the terminaldevice switching between the idle mode of operation and the connectedmode of operation.

Paragraph 17. The method of any one of paragraphs 1 to 16, furthercomprising repeatedly performing the steps of making a measurement ofradio channel conditions for radio resources within the second frequencyband in accordance with the measurement configuration and determining ifthe measurement meets a trigger criterion, and if so, transmitting ameasurement report to the network infrastructure equipment in accordancewith a monitoring schedule.

Paragraph 18. The method of any one of paragraphs 1 to 17, wherein thesecond frequency band comprises radio resources which are shared withwireless communication devices that are not part of the wirelesstelecommunications system.

Paragraph 19. The method of paragraph 18, wherein the wirelesstelecommunications system is configured to operate in accordance with afirst wireless communications operating standard and the wirelesscommunication devices that are not part of the wirelesstelecommunications system are configured to operate in accordance with asecond wireless communications operating standard that is different fromthe first wireless communications operating standard.

Paragraph 20. The method of paragraph 19, wherein the first wirelesscommunications operating standard is a cellular telecommunicationsoperating standard and the second wireless communications operatingstandard is a non-cellular telecommunications operating standard.

Paragraph 21. A terminal device for use in a wireless telecommunicationssystem configured to support communications between networkinfrastructure equipment and terminal devices using a primary componentcarrier operating on radio resources within a first frequency band and asecondary component carrier operating on radio resources within a secondfrequency band, wherein the wireless telecommunications system supportsa connected mode of operation in which terminal devices receiveuser-plane data from the network infrastructure equipment using theprimary and/or secondary component carrier and an idle mode of operationin which terminal devices do not receive user-plane data from thenetwork infrastructure equipment, wherein the terminal device comprisesa controller unit and a transceiver unit configured to operate togetherto: establish a measurement configuration for making measurements ofradio channel conditions for radio resources within the second frequencyband; make a measurement of radio channel conditions for radio resourceswithin the second frequency band in accordance with the measurementconfiguration while the terminal device is operating in the idle mode;determine if the measurement of radio channel conditions meets a triggercriterion, and if so, transmit a measurement report to the networkinfrastructure equipment to indicate the trigger criterion has been met.

Paragraph 22. Circuitry for a terminal device for use in a wirelesstelecommunications system configured to support communications betweennetwork infrastructure equipment and terminal devices using a primarycomponent carrier operating on radio resources within a first frequencyband and a secondary component carrier operating on radio resourceswithin a second frequency band, wherein the wireless telecommunicationssystem supports a connected mode of operation in which terminal devicesreceive user-plane data from the network infrastructure equipment usingthe primary and/or secondary component carrier and an idle mode ofoperation in which terminal devices do not receive user-plane data fromthe network infrastructure equipment, wherein the circuitry comprises acontroller element and a transceiver element configured to operatetogether to: establish a measurement configuration for makingmeasurements of radio channel conditions for radio resources within thesecond frequency band; make a measurement of radio channel conditionsfor radio resources within the second frequency band in accordance withthe measurement configuration while the terminal device is operating inthe idle mode; determine if the measurement of radio channel conditionsmeets a trigger criterion, and if so, transmit a measurement report tothe network infrastructure equipment to indicate the trigger criterionhas been met.

Paragraph 23. A method of operating network infrastructure equipment ina wireless telecommunications system configured to supportcommunications between the network infrastructure equipment and terminaldevices using a primary component carrier operating on radio resourceswithin a first frequency band and a secondary component carrieroperating on radio resources within a second frequency band, wherein thewireless telecommunications system supports a connected mode ofoperation in which terminal devices receive user-plane data from thenetwork infrastructure equipment using the primary and/or secondarycomponent carrier and an idle mode of operation in which terminaldevices do not receive user-plane data from the network infrastructureequipment, wherein the method comprises: communicating user plane-datawith a first terminal device operating in the connected mode using theprimary and/or secondary component carrier; configuring a secondterminal device to make a measurement of radio channel conditions forradio resources within the second frequency band while the secondterminal device is operating in the idle mode and to determine if themeasurement of radio channel conditions meets a trigger criterion, andif so, transmit a measurement report to the network infrastructureequipment to indicate the trigger criterion has been met; receiving ameasurement report from the second terminal device indicating the secondterminal device has determined the measurement of radio channelconditions met the trigger criterion; and modifying the communication ofuser-plane data with the first terminal device using the primary and/orsecondary component carrier in response thereto.

Paragraph 24. Network infrastructure equipment for use in a wirelesstelecommunications system configured to support communications betweenthe network infrastructure equipment and terminal devices using aprimary component carrier operating on radio resources within a firstfrequency band and a secondary component carrier operating on radioresources within a second frequency band, wherein the wirelesstelecommunications system supports a connected mode of operation inwhich terminal devices receive user-plane data from the networkinfrastructure equipment using the primary and/or secondary componentcarrier and an idle mode of operation in which terminal devices do notreceive user-plane data from the network infrastructure equipment;wherein the network infrastructure equipment comprises a controller unitand a transceiver unit configured to operate together to: communicateuser plane-data with a first terminal device operating in the connectedmode using the primary and/or secondary component carrier; configure asecond terminal device to make a measurement of radio channel conditionsfor radio resources within the second frequency band while the secondterminal device is operating in the idle mode and to determine if themeasurement of radio channel conditions meets a trigger criterion, andif so, transmit a measurement report to the network infrastructureequipment to indicate the trigger criterion has been met; receive ameasurement report from the second terminal device indicating the secondterminal device has determined the measurement of radio channelconditions met the trigger criterion; and modify the communication ofuser-plane data with the first terminal device using the primary and/orsecondary component carrier in response thereto.

Paragraph 25. Circuitry for a network infrastructure equipment for usein a wireless telecommunications system configured to supportcommunications between the network infrastructure equipment and terminaldevices using a primary component carrier operating on radio resourceswithin a first frequency band and a secondary component carrieroperating on radio resources within a second frequency band, wherein thewireless telecommunications system supports a connected mode ofoperation in which terminal devices receive user-plane data from thenetwork infrastructure equipment using the primary and/or secondarycomponent carrier and an idle mode of operation in which terminaldevices do not receive user-plane data from the network infrastructureequipment; wherein the circuitry comprises a controller element and atransceiver element configured to operate together to: communicate userplane-data with a first terminal device operating in the connected modeusing the primary and/or secondary component carrier; configure a secondterminal device to make a measurement of radio channel conditions forradio resources within the second frequency band while the secondterminal device is operating in the idle mode and to determine if themeasurement of radio channel conditions meets a trigger criterion, andif so, transmit a measurement report to the network infrastructureequipment to indicate the trigger criterion has been met; receive ameasurement report from the second terminal device indicating the secondterminal device has determined the measurement of radio channelconditions met the trigger criterion; and modify the communication ofuser-plane data with the first terminal device using the primary and/orsecondary component carrier in response thereto.

REFERENCES

-   [1] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based    radio access”, John Wiley and Sons, 2009-   [2] ETSI TS 136 211 V 11.5.0 (2014-01)/3GPP TS 36.211 version 11.5.0    Release 11-   [3] ETSI TS 136 212 V 11.4.0 (2014-01)/3GPP TS 36.212 version 11.4.0    Release 11-   [4] ETSI TS 136 213 V 11.6.0 (2014-03)/3GPP TS 36.213 version 11.6.0    Release 11-   [5] ETSI TS 136 321 V 11.5.0 (2014-03)/3GPP TS 36.321 version 11.5.0    Release 11-   [6] ETSI TS 136 331 V 11.7.0 (2014-03)/3GPP TS 36.331 version 11.7.0    Release 11

1. A method of operating a terminal device in a wirelesstelecommunications system configured to support communications betweennetwork infrastructure equipment and terminal devices using a primarycomponent carrier operating on radio resources within a first frequencyband and a secondary component carrier operating on radio resourceswithin a second frequency band, wherein the wireless telecommunicationssystem supports a connected mode of operation in which terminal devicesreceive user-plane data from the network infrastructure equipment usingthe primary and/or secondary component carrier and an idle mode ofoperation in which terminal devices do not receive user-plane data fromthe network infrastructure equipment, wherein the method comprises:establishing a measurement configuration for making measurements ofradio channel conditions for radio resources within the second frequencyband; making a measurement of radio channel conditions for radioresources within the second frequency band in accordance with themeasurement configuration while the terminal device is operating in theidle mode; determining if the measurement of radio channel conditionsmeets a trigger criterion, and if so, transmitting a measurement reportto the network infrastructure equipment to indicate the triggercriterion has been met.
 2. The method of claim 1, wherein themeasurement configuration is established from signalling received fromthe network infrastructure equipment.
 3. The method of claim 2, whereinthe measurement configuration is established from system informationsignalling broadcast by the network infrastructure equipment to aplurality of terminal devices.
 4. The method of claim 2, wherein themeasurement configuration is established from dedicated signallingtransmitted from the network infrastructure equipment to the terminaldevice.
 5. The method of claim 1, further comprising the terminal deviceswitching from the idle mode of operation to the connected mode ofoperation to transmit the measurement report to the networkinfrastructure equipment.
 6. The method of claim 1, wherein themeasurement configuration is associated with one or more measurementobjects specifying the radio resources within the second frequency bandin respect of which the measurement of radio channel conditions is to bemade.
 7. The method of claim 1, wherein the radio resources in respectof which the measurement of radio channel conditions is made areassociated with one or more frequency channels on which the secondarycomponent carrier may operate in the second frequency band.
 8. Themethod of claim 1, wherein the measurement of radio channel conditionscomprises one or more measurements selected from the group comprising:(i) a measurement of a received power for reference signals transmittedby the network infrastructure equipment on the secondary componentcarrier; (ii) a measurement of a received quality for reference signalstransmitted by the network infrastructure equipment on the secondarycomponent carrier; and (iii) a measurement of a signal strength receivedby the respective terminal devices on the radio resources.
 9. The methodof claim 1, wherein determining if the measurement of radio channelconditions meets the trigger criterion comprises determining if a levelof radio interference determined from the measurement of radio channelconditions exceeds a predefined threshold value.
 10. The method of claim1, wherein determining if the measurement of radio channel conditionsmeets the trigger criterion comprises determining if the networkinfrastructure equipment is transmitting on radio resources whichoverlap with radio resources being used by a wireless communicationsdevice operating within a coverage area of radio transmissions from thenetwork infrastructure equipment.
 11. The method of claim 10, whereinthe wireless communications device is the terminal device itself. 12.The method of claim 1, wherein the measurement configuration comprisesone or more indications selected from the group comprising: (i) anindication of the radio resources in respect of which the measurement ofradio channel conditions is to be made; (ii) an indication of when themeasurement of radio channel conditions is to be made; (iii) anindication of how the measurement of radio channel conditions is to bemade; and (iv) an indication of the trigger criterion.
 13. The method ofclaim 1, further comprising the terminal device switching from theconnected mode of operation to the idle mode of operation afterestablishing the measurement configuration for making measurements ofradio channel conditions and before making the measurement of radiochannel conditions while the terminal device is operating in the idlemode.
 14. The method of claim 1, further comprising the terminal deviceswitching from the idle mode of operation to the connected mode ofoperation after making the measurement of radio channel conditions whilethe terminal device is operating in the idle mode and making one or moremeasurements of radio channel conditions for radio resources within thesecond frequency band in accordance with the measurement configurationwhile the terminal device is operating in the connected mode.
 15. Themethod of claim 1, further comprising the terminal device establishingan updated measurement configuration for making measurements of radiochannel conditions for radio resources within the second frequency band;making a further measurement of radio channel conditions for radioresources within the second frequency band in accordance with theupdated measurement configuration; determining if the furthermeasurement of radio channel conditions meets a trigger criterionassociated with the updated measurement configuration, and if so,transmitting a measurement report to the network infrastructureequipment to indicate this.
 16. The method of claim 15, wherein theupdated measurement configuration is established in response to theterminal device switching between the idle mode of operation and theconnected mode of operation.
 17. The method of claim 1, furthercomprising repeatedly performing the steps of making a measurement ofradio channel conditions for radio resources within the second frequencyband in accordance with the measurement configuration and determining ifthe measurement meets a trigger criterion, and if so, transmitting ameasurement report to the network infrastructure equipment in accordancewith a monitoring schedule.
 18. The method of claim 1, wherein thesecond frequency band comprises radio resources which are shared withwireless communication devices that are not part of the wirelesstelecommunications system.
 19. The method of claim 18, wherein thewireless telecommunications system is configured to operate inaccordance with a first wireless communications operating standard andthe wireless communication devices that are not part of the wirelesstelecommunications system are configured to operate in accordance with asecond wireless communications operating standard that is different fromthe first wireless communications operating standard.
 20. The method ofclaim 19, wherein the first wireless communications operating standardis a cellular telecommunications operating standard and the secondwireless communications operating standard is a non-cellulartelecommunications operating standard.
 21. A terminal device for use ina wireless telecommunications system configured to supportcommunications between network infrastructure equipment and terminaldevices using a primary component carrier operating on radio resourceswithin a first frequency band and a secondary component carrieroperating on radio resources within a second frequency band, wherein thewireless telecommunications system supports a connected mode ofoperation in which terminal devices receive user-plane data from thenetwork infrastructure equipment using the primary and/or secondarycomponent carrier and an idle mode of operation in which terminaldevices do not receive user-plane data from the network infrastructureequipment, wherein the terminal device comprises a controller unit and atransceiver unit configured to operate together to: establish ameasurement configuration for making measurements of radio channelconditions for radio resources within the second frequency band; make ameasurement of radio channel conditions for radio resources within thesecond frequency band in accordance with the measurement configurationwhile the terminal device is operating in the idle mode; determine ifthe measurement of radio channel conditions meets a trigger criterion,and if so, transmit a measurement report to the network infrastructureequipment to indicate the trigger criterion has been met.
 22. Circuitryfor a terminal device for use in a wireless telecommunications systemconfigured to support communications between network infrastructureequipment and terminal devices using a primary component carrieroperating on radio resources within a first frequency band and asecondary component carrier operating on radio resources within a secondfrequency band, wherein the wireless telecommunications system supportsa connected mode of operation in which terminal devices receiveuser-plane data from the network infrastructure equipment using theprimary and/or secondary component carrier and an idle mode of operationin which terminal devices do not receive user-plane data from thenetwork infrastructure equipment, wherein the circuitry comprises acontroller element and a transceiver element configured to operatetogether to: establish a measurement configuration for makingmeasurements of radio channel conditions for radio resources within thesecond frequency band; make a measurement of radio channel conditionsfor radio resources within the second frequency band in accordance withthe measurement configuration while the terminal device is operating inthe idle mode; determine if the measurement of radio channel conditionsmeets a trigger criterion, and if so, transmit a measurement report tothe network infrastructure equipment to indicate the trigger criterionhas been met.
 23. A method of operating network infrastructure equipmentin a wireless telecommunications system configured to supportcommunications between the network infrastructure equipment and terminaldevices using a primary component carrier operating on radio resourceswithin a first frequency band and a secondary component carrieroperating on radio resources within a second frequency band, wherein thewireless telecommunications system supports a connected mode ofoperation in which terminal devices receive user-plane data from thenetwork infrastructure equipment using the primary and/or secondarycomponent carrier and an idle mode of operation in which terminaldevices do not receive user-plane data from the network infrastructureequipment, wherein the method comprises: communicating user plane-datawith a first terminal device operating in the connected mode using theprimary and/or secondary component carrier; configuring a secondterminal device to make a measurement of radio channel conditions forradio resources within the second frequency band while the secondterminal device is operating in the idle mode and to determine if themeasurement of radio channel conditions meets a trigger criterion, andif so, transmit a measurement report to the network infrastructureequipment to indicate the trigger criterion has been met; receiving ameasurement report from the second terminal device indicating the secondterminal device has determined the measurement of radio channelconditions met the trigger criterion; and modifying the communication ofuser-plane data with the first terminal device using the primary and/orsecondary component carrier in response thereto. 24-25. (canceled)